Mafia 2 (very much like GTA but not quite as sandboxy unfortunately) it's a very good-looking and cinematic game. voice acting is top notch, the whole game feels like an interactive godfather movie. very well-done, authentic atmospheres to each of the time periods you play durin, and both the driving and shooting gameplay feels pretty solid. def play it on hard though because its a walk in the park on normal.
Killing Floor - PC only co-op zombie killing at its finest. i have all my perks leveled up to max, but still play this regularly since it came out last april.
http://www.youtube.com/watch?v=5FZTXWfE11U
assassins creed 2 - on back burner because i got but out on it because its so repetitive, seems to be common in most of ubis recent titles
previous favorites:
dragon age - best RPG i've played in a long time. take a couple hours to pick up, but the other ~30-40 hours are pure, classic bioware awesomeness.
resident evil 5 - i wish the games would return to being dark and horror instead of daytime action movie BS, but its still fun on co-op.
borderlands - a FPS online co-op RPG, nuff said.
looking forward to:
Guildwars 2 - check out the dev walkthroughs on gametrailers. im not really into MMOs, but i'm def picking this one up. they're trying to make a more persistent online world for players to explore, rather than just creating instances for each specific party. i.e. you're running around outside city doing a quest and you see other players working together to complete real time events and other shit while you're out doing so. full day/night cycle, and much better looking combat than the first.
The Old Republic - As poster above me said, its knights of the old republic online. more bioware awesomeness.
Crysis 2