A really mixed bag
Mass Effect 3 is a really strange game. There's an undeniable amount of polish to it - famous voice actors, big set pieces, fluid controls, and some quality story telling. However, that's weighed against some spotty writing, short content and what appears to be cut-corners.
ME3 starts a few months after ME2, with Shepard having once again lost his crew and his ship. The reason why Shepard is in this predicament is only explained by a bit of ME2 DLC, which is not a great way of starting off your game to be perfectly honest. Anyway, Bad Guys show up, Shepard gets the hell away on his ship and he's back saving the galaxy once again.
The Story is perhaps the most important thing about ME3, which is why I'm not going to go into it. Needless to say, most of it is pretty good. There are a few decisions that BioWare has made which I find questionable (EDI/Ninja-Man/That-Damn-Kid) but for the most part it's pretty good. The writing seems to be very solid for 70% of the game, however it dips (badly) during the first part of the game and the last section of the game. The story also has an ending which will please only a few, disappoint many (including me) and enrage yet even more. No, despite what you've heard it is NOT the "Worst Ending In The World" (Kane & Lynch 2's ending still take's that cake), but it is poor in terms of choice, in terms of length and in terms of clarity. It gives very little closure to the series. Honestly, a lot of you are going to be disappointed by how abrupt, deus-ex-like and sudden the ending is. It's not necessarily WHAT happens, it's HOW it's told, it's how short it is, it's how lacking in substance it is.
But still, 70~80% of the story is pretty goddamn great, especially if you've played ME2 with all your squad members alive. Main Missions (called Priority Missions) are almost universally excellent in length and quality. However, there aren't many of them. A lot of ME3's side-quests are extremely poor. 90% of them are nothing more than DA2 style "Go here, get this, return to man/woman/alien on citadel who is stuck in a permanent conversation loop" Another other 5% are side quests which are really just part of the priority quests and these are great, if a little short. The last 5% are simply Multiplayer matches that have been toned down and re-purposed as "single player" missions. This is a great disappointment, given the GIGANTIC quantity and quality of the side-quests in ME2. There is also no vehicle based exploration, which is very disappointing given the possibilities presented in ME2's DLC.
Gameplay is fine - it's ME2 with slightly more clever/aggressive enemies, a few new powers and the ability to roll and perform very minor, scripted jumps. If you had no problems with ME2's combat, you'll have no problems with ME3's combat. If you didn't like ME2's combat, then brace yourself for more of the same. The classes are there, the powers are there, the mechanics are almost identical to ME2's, save two things:
1) You can "evolve" powers after a certain point - accumulate enough points into a skill and you are presented with two branching paths (although you can switch between the branches at any time) leveling up your powers in slightly different ways. Do you want your shockwave to travel further? Or do you want it to be wider? Do you want adrenaline boost to do more damage? Or do you want it to recharge faster? Do you want stronger disruptor ammo? Or do you want your squad to gain disruptor ammo (albeit at only 50% the effectiveness of yours)?
2) There's a "Far-Cry 2", "Resistance: Fall of Man" style health regeneration. You still have your shields and they'll always recharge (and fairly quickly) if you are out of fire. However, your health bar is separated into five segments - and if you lose a segment, you can't get it back until the end of the mission or until you use a medi-gel. If your segment is only half gone, it'll recharge that segment fully - but not any segment that you've fully lost. This might seem interesting, except that medi gel is so abundant that it isn't anything to stress over.
In terms of Graphic and Sound, ME3 looks and sounds good. It's not a fantastic leap over ME2, but you can tell it looks slightly better (even if they use many of the art-assets from ME2, and a lot of the same NPC faces). The Music is good enough, but not as memorable as ME2's (and they re-use most of ME2's soundtrack anyway).
Over all, ME3 is a good game. But it's not as good as ME2, not by a long shot. It honestly feels as if they cut corners and didn't put as much effort into the game. It's still worth your money, but be aware that it's the weakest of the trilogy in terms of story, and it never surpasses it's predecessor, ME2.
Oh and the muliplayer's alright. Just alright. Nothing special. Nothing you'd want to play for more than a weekend or two.
EDIT: 26th of June, 2012
I thought I'd just add in my opinion of the free ME3 Ending DLC. After the tremendously negative and vocal fan feedback (which I understood and sympathized with, but didn't totally share) BioWare stalled progress on all future DLC and went to work making this ending DLC instead. They even hired back some (not all) of the voice actors to record lines. So, how did they do?
As good a job as they could - I'm not going to spoil the endings, that's not the point of the review. Does it change the score I gave it? No, not really. The endings do improve somewhat on the three ME3 endings, but perhaps not enough to sate the really angry fans.
