Complaints is why Mass Effect 2 plays so much better than Mass Effect 1.  
 
I think we should complain about RDR (because it gets plenty of well-earned praise, what with it being GOTY and all) and let's get ourselves a perfecter sequel: 
 

1. Less getting hung up on door jambs and other stuff. Use Euphoria for an even higher degree of limb interaction with nearby objects. In Real Life™ (IRL ™) people brush their hands off of walls when running next to them for guidance and stability. Backbreaker shows us that NaturalMotion is making great leaps in realistic limb interaction, weight shifting, inertia and locomotion of in-game humans. I'm confident Rockstar Sand Diego will keep on making it more and more true to life (and still fun).
2. Horses that don't leap to their death when left alone near a cliff

3. Better economy. At some point money is no longer meaningful and the player has nothing worthwhile to buy. The economy needs to be better balanced in future games so that there's always something new and useful to purchase at game stores.
 4. Immediate challenge rewards. Rather than making a player go through a ton of challenges before receiving rewards, start giving them out right away. Unique weapons, items, horses, RPG-esque ability buffs are all great and makes the work to the maximum challenge level more meaningful and makes the grinding feel like less than it is.
5. Train robberies. Why the hell is this not in the game already?
6. Make skinning worthwhile. If I'm going to skin every animal alive, I'd like it to contribute to something other than a few dollars. If it's just meant to be sold then have it automatically sell, otherwise have it contribute to something e.g. an outfit. One way to make this somewhat more interesting is to break up the outfit into pieces and then use furs and skins from various animals to make yourself an outfit of various hides.

7. No more outfits, just items you can purchase / find and equip instead of full sets. (fx why cant i wear the mexican hat with my legend of the west outfit etc.)

All I want is a more flushed out online mode. Make it more like an MMO (or at least what I imagine an MMO game to be like).
  
This game is otherwise excellent in my book.

More understandable motivations for each specific mission, and a wider range of dialogue for the main character besides 'I'm lookin fer 2 dewds!'. God freakin dammit, Marston, we get it already!

More work done to catch all those annoying glitches, like when you're picking up a hog-tied bounty, your character picks up an invisible guy and can't put him down again, or you can, but the image-picture of him stays on the ground. I was like wtf?

" All I want is a more flushed out online mode. Make it more like an MMO (or at least what I imagine an MMO game to be like).  This game is otherwise excellent in my book. "

12. Melee for when someone runs up in your face (different than the knife). I'm talking a gun butt to the face just to get someone off you. Too many times (in either multi or single player) someone gets so close to me that I can't even get my gun on them. In real life a person would just elbow or gun butt their attacker.

" @MysteriousBob said:

" All I want is a more flushed out online mode. Make it more like an MMO (or at least what I imagine an MMO game to be like).  This game is otherwise excellent in my book. "

The online mode is the biggest surprise for me.   Having more players and more modes (stagecoach - defend or attack) would be a great addition.  The PvP (Posse vs) is a lot of fun. Was part of a full posse, and this guy logs in and starts killing on the members.  This is followed by 20 minutes of the entire posse hunting him down each time he spawns, fully coordinated via voice chat. "

I want the D-pad to actually do something useful. Instead of just down to make the tiny shitty map tinier and shittier, how about we have down to select the last used rifle left for the lasso, and right for the last used pistol. I hate the fact that the radial menu doesn't pause the game, riding a horse, trying to keep an eye on a bandit and having to fumble around for a lasso in a pain in the arse.
 
Also I can't work out why the backpack is on the back button, why would I ever need a hotkey for inventory? Yet the journal and map are in the start menu.
 
Lastly the multiplayer menus and game cycling is a confusing mess. Since they want free roam to be kind of a hub, how about having a Burnout Paradise style online system (arguably the best thing about that game was it's online setup).

I want less animations. There doesn't have to be a tiny animation for everything I do.

" More understandable motivations for each specific mission, and a wider range of dialogue for the main character besides 'I'm lookin fer 2 dewds!'. God freakin dammit, Marston, we get it already! "

" @schizogony: Close range shooting kills usually initiate an execute attack that one hit kills the target.  Unless I'm mistaken, the knife is in the game to allow for stealth kills which is something a gun butt is probably less efficient at. "

I would've completely gutted the online mode and expanded single player even further. But that's just me.

13?. Less mashing X to run.

more freedom in outfit customization ,not too much,but I would love to have the option to choose from several hats,boots,etc.
 
an option to skip skinning animations

" more freedom in outfit customization ,not too much,but I would love to have the option to choose from several hats,boots,etc.  an option to skip skinning animations "