The games I bought this year are:
-Warhammer 40,000: Dawn of War II: Chaos Rising
I loved this game even more than I did the first. The new units were a loads of fun to use, and the Chaos faction really added a lot of flavor to the game with the worship mechanics. The campaign was (IMO) very fun, and definitely better than the first.
-Mass Effect 2
This game was amazing. The combat wasn't all that fun and the RPG elements were trimmed, but the production quality and the sense that my choices actually meant something made this game worth it. Very few games I play through twice, let alone wanting to play a third.
I absolutely love this game. Admitadly I haven't played it in months now, but I am sucha huge fan of Blizzard RTSs and this game truely delivered. The campaign was awesome with it's blizzard cinematics, mission variety, army customization, and more. And just by the name the MP doesn't even need to be mentioned.
-Fallout: New Vegas
I had a lot of fun with this game(and about 60 hours). It really improved on almost the entirety of Fallout 3 with it's voice acting, gun variety, actual choices, gray areas, ect.
I didn't actually buy this one but it came free with my processor and I never played it
Didn't buy this one either, but it was very fun before we all figured out they aren't going to add more campaigns.
I bought this with the Orange Box, played it, got it for free on Steam, played it again.
-Grand Theft Auto: Vice City
I played this one as a kid(I know, I know) so when I saw it for two bucks I couldn't resist.
-Team Fortress 2
I've owned this for a while but I bought it for my current Steam account on like the 31st of last year on sale.
-Sins of a Solar Empire [Expansions]
These are an absolute must buy for any sins fan. My brother and I probably exponentially increased our time clocked in Sins once we got the expansions.
Maybe something else? Who knows?