With good reason my GOTY as well as GB's, I fucking love this game. And still, some things can be made even better. Here's what I'd really want Bioware to for the next one:
 
No Mining - Still being able to explore planets, but only to look for secret missions which in turn should have more than enough resources scattered around. Still be able to find them on regular missions, but much more rarely and only enough to get you upgrades for playing through on normal/veteran.
 
More variety in main missions - If need be have a smaller team, but my point is less focus on recruiting. Given the opportunities with the environment and situation in ME3, I'm hoping they will mix things up properly.
 
Collateral Damage - Killing more than one enemy with a single bullet. A strange omission in ME2 I found quite puzzling. Also, I want achievements for it like:
 
Collateral - kill 2 enemies with one bullet (no wai) - 20 G
Collateral Threesome - kill 3 enemies with one bullet (wut?) - 30 G
Collateral Foursome - kill 4 enemies with one bullet (OMFG) - 40 G
 
EDIT: Forgive my stupidity, should have posted this in ME3 forum. :(

You've already recruited a team, I doubt they'll make you do that whole thing again. Not saying there won't be any new team additions or anything, but I doubt there will be as much emphasis around building a team, especially as that was a big part of 2's story. 
 
And those lame achievements will turn it into even less of an RPG, which is the wrong way, they should make it even more of an RPG. Fuck dumbing it down.

1.  Side stories focus both on the individual team mates as well as progress the overall story, more like ME1.
2.  Mining is made less like a chore.
3.  Bring back some sort of looting system.  I doubt they'll go back to ME1 with all the various level of weapons, but would be nice to see lootable technologies that could be used to swap in and out weapon/armor enhancements that drop off mini and main boss creatures in each area at least.
4.  Bring back N+ gaming with expanded skill ranks and higher level gear based on the level of difficulty rather than just carrying over your characters level and having to find all of the upgrades all over again.
 
@AlexW00d said:

" You've already recruited a team, I doubt they'll make you do that whole thing again. "

" You've already recruited a team, I doubt they'll make you do that whole thing again. Not saying there won't be any new team additions or anything, but I doubt there will be as much emphasis around building a team, especially as that was a big part of 2's story.  And those lame achievements will turn it into even less of an RPG, which is the wrong way, they should make it even more of an RPG. Fuck dumbing it down. "

More main story missions, less not-main-story missions.

Inventory would be nice. Not having to go back to my ship or some other place to change my armor or whatnot.
 
Melee. I would love some power hammers or something for my big Damage soakers. Not really for my Shepard but a Melee spec for a Kroagan or a Biotic who specializes in melee combat would be neat. Would be great to send them in while i pick the enemies off with my sniper.
 
No mining or resource gathering please. Money as a concept for buying things works surprisingly well. Just make shit give more money or let me potentially grind out some money if i really want some primo stuff. 
 
The cosmetic helmet option would be great. This is an RPG still. Supposedly. Just more customization for my dude or lady overall would be very nice. Maybe more templates of real people that can be slightly customized so my Shepard doesn't look like some plastic freak with plastic hair.

Fucking loot God dammit.

Agreed with the loot.
 
And more exploration too.

" Not really for my Shepard but a Melee spec for a Kroagan or a Biotic who specializes in melee combat would be neat. "

This is more knit picking  
1. Revamp the Mining, making it automated? or do not have it at all 
2. Revamp Loot System 
3. Improve Facial Animation and Character Body Movement in dialogue (Less manikin like)  
quality of the Custom Faces  (Like Jeff Said, Face Scanning, I CAN be Shepard?!)
4. Solve the helmet problem 
5. More Weapon types, close-combat weapons? 

The only thing I want is more RPG-Elements. Mass Effect 2 was an amazing game, just not an amazing RPG. 

 - More interesting mission level layout.  In fact I'd say that a lot of mission levels have really boring layouts, e specially when playing though a second time. 
- A little more variety the various level assets (like doors - both openable and un-openable, plants, tables, chair etc) 
- A better way to collect minerals 
- More people wondering around in the open areas
- Make the Citadel at least as interesting to visit as in ME1 
- Sprinting feels a little clunky
 - Put a little more in the open areas, to make them feel more like a real place 
- Music calls a little flat, especially compared to the first game 
- Walking around the Normandy should not need any loading screens  
- Would be nice if team members stopped constantly getting right in-front of me during fight scenes 
- Show me more of the cool shit out of the windows.  I want to see some cars flying around. 
- Make the worlds feel a little dirtier, everything seems so pristine and fake

- More loot 
-Weapon customization 
-More impressive biotic powers 
-Normandy Stays docked and takes off until you say so 
-Better team AI and possibility for more squadmembers (3,4) 
-No dumb hacking minigames 
-Toggle helmet 
-Better character model for Miranda 
-more sex

" @AlexW00d said:

" You've already recruited a team, I doubt they'll make you do that whole thing again. Not saying there won't be any new team additions or anything, but I doubt there will be as much emphasis around building a team, especially as that was a big part of 2's story.  And those lame achievements will turn it into even less of an RPG, which is the wrong way, they should make it even more of an RPG. Fuck dumbing it down. "

I guess I'm the only dude who wants to see RPG elements decrease D:  Okay, but at least have ONE collateral achievement won't hurt, right? "

" @JoyfullOFrockets said:

" @AlexW00d said:

" You've already recruited a team, I doubt they'll make you do that whole thing again. Not saying there won't be any new team additions or anything, but I doubt there will be as much emphasis around building a team, especially as that was a big part of 2's story.  And those lame achievements will turn it into even less of an RPG, which is the wrong way, they should make it even more of an RPG. Fuck dumbing it down. "

I guess I'm the only dude who wants to see RPG elements decrease D:  Okay, but at least have ONE collateral achievement won't hurt, right? "

Only if it is with the Heavy Weapons. One hit kills in a partially RPG like Shooter are completely out of the question. Just play GoW if you want that shit. "

" @AlexW00d said:

" @JoyfullOFrockets said:

" @AlexW00d said:

" You've already recruited a team, I doubt they'll make you do that whole thing again. Not saying there won't be any new team additions or anything, but I doubt there will be as much emphasis around building a team, especially as that was a big part of 2's story.  And those lame achievements will turn it into even less of an RPG, which is the wrong way, they should make it even more of an RPG. Fuck dumbing it down. "

I guess I'm the only dude who wants to see RPG elements decrease D:  Okay, but at least have ONE collateral achievement won't hurt, right? "

Only if it is with the Heavy Weapons. One hit kills in a partially RPG like Shooter are completely out of the question. Just play GoW if you want that shit. "

And I think by GoW, Alex means Gears of War and not God of War :p "

" @cgoodno said:

" @AlexW00d said:

" @JoyfullOFrockets said:

" @AlexW00d said:

" You've already recruited a team, I doubt they'll make you do that whole thing again. Not saying there won't be any new team additions or anything, but I doubt there will be as much emphasis around building a team, especially as that was a big part of 2's story.  And those lame achievements will turn it into even less of an RPG, which is the wrong way, they should make it even more of an RPG. Fuck dumbing it down. "

I guess I'm the only dude who wants to see RPG elements decrease D:  Okay, but at least have ONE collateral achievement won't hurt, right? "

Only if it is with the Heavy Weapons. One hit kills in a partially RPG like Shooter are completely out of the question. Just play GoW if you want that shit. "

And I think by GoW, Alex means Gears of War and not God of War :p "

Mmm from what I recall Gears don't have collaterals. :/ "

 Yeah they should fix the UI which looked a little cheap in ME2. They should make the Normandy stay docked until you want to leave like in ME1, maybe try and get rid of some of the loading screens in the game, allow me to install all the discs and play off of one and fix Miranda's face. The biggest question is what to do with the planet exploring stuff. People didn't like the Mako (although I didn't mind it) and the planet scanning was dull, so for them that would be the biggest thing to fix and probably the hardest. I will say though after playing ME2 I could  take or leave an inventory system they would probably be fine just making the upgrade stuff a little more customizable. 

" @JoyfullOFrockets said:

" @cgoodno said: 

And I think by GoW, Alex means Gears of War and not God of War :p "

Mmm from what I recall Gears don't have collaterals. :/ "

I wouldn't know, only played a bit of the first one and wasn't interested in what I experienced. "

" @cgoodno said:

" @JoyfullOFrockets said:

" @cgoodno said: 

And I think by GoW, Alex means Gears of War and not God of War :p "

Mmm from what I recall Gears don't have collaterals. :/ "

I wouldn't know, only played a bit of the first one and wasn't interested in what I experienced. "

I've no idea if it does either, I've also never heard it called collateral tbh. I just meant that if you want a more third person shooter experience, play a Third person Shooter. Mass Effect needs to be more RPG >:) "

-helmet off while talking in cut scenes.
 -more side quests that have nothing to do with main story but may offer better loot, upgrades or other devices.  some spice, hidden treasures along the journey.
-better faster loading  (goes for all games) 
-wouldn't mind a more advanced leveling system ala fallout. (no thank you to repairing weapons and gear though)

Volus squad member.
 
Let's do this.

Just make it bigger and better with no tedious mining or planet exploration then I will be happy.  

1. Be able to walk around The Citadel like ME. 
2. Just a general sense of awe that was in ME, that was missing in ME2.

Better hair. The hair looked like it was a solid chunk of plastic or something...

-Some more RPG elements, not as quite heavy as ME1 but still a bit more depth 
-Allow as much customization on armor for your party members as you could with Shepard in 2 (at least)
-Blind firing with better sights/UI
=Have Miranda, Thane, Samara, Mordin, and Legion return as well.  
 
Also, better customization of appearance. I don't really like the hair and face options that much, and you can't even edit the look of the "commercial" Shepard. When you try to it just gives you the Chuck Norris dude. :l

" Volus squad member. Let's do this. "

-better animation with teammates. if you watch your teammates behind you as youre engaging in a conversation with an npc, they make the same jerky animations when you click a dialogue option. the issue is even more glaring when you have human teammates. i used zaeed throughout my second playthrough and he looked like a lifeless mannequin
-a FUN minigame that is somewhat open ended and helps illustrate an open world. i have no idea what this would entail, all i know is that the mining minigame wasn't fun at all 
-a better balance between 3rd person shooting and roleplaying mechanics. i didnt mind  me2's stripped rpg mechanics but i think it would be nice to implement loot/stats in a way that wouldnt hurt the flow of the game 
-more open world feel. basically what brad stated in the goty podcast. the game still felt limited in scope considering what it was attempting to depict, although fixing this would prob just require more effort + manpower

More persistent corpses.
"Heaver" physics.
More weight to the weapons.
A stronger story.
Helmets removed in conversations/other.
More crowded areas.
An inventory.
And more.

More RPG-iness. 
More Exploration. 
Loot/Inventory system. 
Less individual areas but larger ones instead. It seems pointless having whole systems that are unexplorable and are basically just meaningless (but interesting) codex entries. In other words a more focused gameplay area. 
 
What Brad said in the Day 6 GOTY podcast about the ME universe not feeling big really struck a chord with me, make Illium, Omega and the Citadel large, unique areas with plenty to do. (Shops, side quests)

More Blasto the Hanar!!!!!!!!!! 
"This one would like to know if the criminal scum considers itself fortunate"  
 
That commercial was awesome ^^

No regenerating health
 
Ammo types not abilities
 
More guns with more stats (not just 'excellent against armor, weak against shields")
 
Ability to control squad mates
  
Planetary exploration with the Hammerhead (resource collection like ME1, but give you the ability to upgrade weapons/armor)
 
 Upgrades should make you feel like you're stronger

I'm surprised no one mentioned this. I hope they make the relationships between comrades feel more organic, in the same style as Alpha Protocol. The socializing mechanic from ME and ME2 traces back to 2003's Knights of the Old Republic. Bring something better to the table than that same tired and mechanical system. And change Garrus' line of "Can it wait for a bit longer? I'm calibrating the cannons.", or at least give the option to either punch him in the face or shoot him. 

i want an rpg

" @Jeust: IMO its a little worse then KOTOR as you could at least talk to your party while in missions.  I wouldn't want any of the heavy personal dialog to be available during missions (romancing Bastila in the middle of a Tusken Raider camp makes no sense imo!)  but it would be nice to be able to ask them things about the planet or what they think we should be doing next, similar to the original KOTOR's "What do you know about this planet?".  Or atleast a return to ME 1's random responses depending on where you were.  I found there weren't enough 'points of interest' in ME2 were your squad mates would speak up during missions. "

Mass Effect 2 was such an improvement from the first game, but I don't want Bioware to think that it means they can make Mass Effect 3 without changing much.  
 
They should further improve the combat. I'm not saying it wasn't good, but it wasn't the best 3rd-person cover based shooter and can be improved. 
I'd like to see a return of some of the RPG mechanics. 
Make it so that doing a full install lets me use only one disc, because Mass Effect 3 is definitely going to have at least 2.
And for the love of god, please put back in the helmet toggle from the first game. Whoever thought it was a good idea to remove that is crazy.

OhInventory - Add one back please. Also bring back deeper team character customization. I spent the entire game raging about the fact that  I basically had unlimited resources and all the credits I could ever want, but I couldn't even get Garrus a damn suit without a giant hole in it! "

I want some loot damnit.  And bring back the concept of multiple playthroughs required to get max level.  It might be the love of the grind in me but that shit gets me excited as hell.  Knowing I can get my Shepard stronger than most other players will and that there might always be some improved armor or gun drop in the next mission just keeps me hooked and on the edge of my seat the whole time.  Its the same reason I played d2 all those years, a bit of that in Mass Effect makes it perfect.  ME1 nearly got it right so lets perfect it in ME3.

" Fucking loot God dammit. "

The problem is once you go full retard, you never come back; so I doubt they'll re-complicate things after having simplified ME2 and selling asstons. 

• More RPG features. Leveling in battles, more levels, more skills to upgrade, etc.   
• Bring the snyth music back. Itwasawesome. Leave the orchestral stuff for the end mission or something.  
• More stuff with the Hammerhead. Lots of platforming potential with it. 
• More animation while talking, like taking off your helmet (if wearing one) while sitting and talking to somebody.  
• Looting stuff off corpses, in chests, etc.  
• More involving side-quests, often on new planets that you haven't been able to visit before.  
• Ability to customize weapons. 
• Bigger environments. Less corridors and such. 

For me, it all boils down to making the main story lengthier   I felt like I spent the entirety of Mass Effect 1 & 2 recruiting characters, only to have the game end shortly thereafter.  Obviously, side missions bulk this up plenty, but I really want a meatier main story with a longer build towards its climactic mission.  

I have a few ideas:
 

• Bring back the loot system in the first ME, however reduce the rate in which you get loot and keep the current customization options in ME2.
• Make new helmets which can open up to see the face of Shephard.  Even with or without the helmet, there should be some clearance for all drinking and kissing scenes to make more sense.
  
• Bring back the old levelling system with more abilities, however let the player choose a couple to add to the hotkey buttons for consoles like they do in ME2 (I believe it is handled that way on console, only have PC version here).  I didn't like the lack of abilities for my Shephard in ME2, resulting in less dynamic combat options and methods.
• Bring back the planet exploration, however improve and use the Hammerhead instead of the Mako.  The Hammerhead is fine but make it feel more like an actual vehicle like the Mako, but without the bad maneuvering of the Mako (Not that I ever had a real problem in the first Mako, as I was able to traverse quite fine).
• Find a way to make mineral-collecting less of a chore via sending ship members to missions, and perhaps incorporate a worker system to get members and freelancers to do some of the more mundane tasks with varying success depending on the quality of the worker sent.
• Bring back the temperature cooling bar for guns in ME1 but allow for reload clips to instantly get back to the fight quicker.  This would allow Bioware to make the clips more valuable as situational things to use when you really need to shoot more.  Having the clips still feels like you are belittling the lore about guns not running out of ammo with the clips alone.
• I don't know how you do it, but one more song from Faunts or some artist to close out ME3 in the credits, like how they closed out ME1 with that awesome song.

Controller support for the PC version. Preferably allow hybrid mode where I can use a mouse in one hand and a controller in the other.

Actual weapon stats. Loot. 
 
The Mako. Fuck this hovercraft shit.

More missons involved with the main story arc.  The loyalty missions were great, but they didn't always move the main plot forward.  Granted, with the trailer showing what it did, I doubt there'd be time to get you promoting shops in the Citadel, etc.
 
Of course, this being a game, they'll probably somehow make time.