Bioshock 2?
Just kidding. It's a decent game but there's better things to catch up on.
I'm not sure on dates so some suggestions may be off. If you haven't payed Mass Effect 1, then do that then play Mass Effect 2.
Batman Arkham Asylum was fantastic and the new one is out soon.
Deux Ex: HR is quite new and lots are having a good time with it, though it's kind of a love it/hate it type of thing it appears.
The Witcher 2 is a great RPG and much improved over the first, and if you never played the first you could jump into 2 pretty easily without missing much.
Fallout: NV is good, and worth playing if you played Fallout 3 or not. If you didn't like Fallout 3 though then it didn't change much.
Also, what kind of horsepower are we dealing with in your PC? Not sure if you'll be able to play things like The Witcher 2 without knowing what you have.