Makes me want to write a blogpost about this... [these aren't in any order other than the order in which they've emerged from my sleepy mind]:
Valkyria Chronicles - a weird mix of Japanese anime/cartoon [no idea of the technical difference] artstyle, slightly too cute except for when you're, er, in a very thin allegory of a Nazi concentration camp, and an interesting mix of strategic and first person shooter, it flew under the radar but was very highly rated. I picked up my copy for about £12, which was a bargain.
Dragon's Dogma - action RPG. Weirdly for an RPG, the story goes missing (it's good at the start and end but just goes walkies for the middle). Voice-acting is very variable. The world's generic. So why buy? The gameplay is ****ing outstanding. Seriously, best RPG combat at least since Vagrant Story, and probably best ever. The character classes genuinely play differently, you create not only your player-character but also your main pawn [think magic slave], and have 2 more, which can be borrowed from other players (and if others borrow your main pawn then you get 'paid' in rift crystals which can be used to buy rare, mostly character customisation items).
XCOM: Enemy Unknown - a near perfect mix of third person tactics/strategy as you control a squad of 4-6 on battlefield maps, and base commander as you make your underground lair just so, XCOM's all about defending Earth from illegal immigrants. Who also kidnap and torture people and are psychotic aliens. Since release there's been a new version with some extra bits/DLC included [I haven't played that version].
Dragon Age: Origins - one of the best RPGs I've ever played. It's got an outstanding cast, a well-realised world and I don't want to write much more because you should play it yourself. And it'll be knock-down cheap by now, probably.
Mass Effect - I came late to this and had some technical issues with the first game [I bought the trilogy version], when it froze right after the final fight (I did discover a way to stop it, decreasing difficulty, removing the automatically implemented graphical filters and not using special abilities in the last fight). However, that glitch aside, the three games, perhaps especially the second, are fantastic. Jennifer Hale is brilliant as Commander Shepard [you can play as a chap, but when I tried that after being Femshep for 3 games it didn't seem to fit for me].