I'm just going to list some games I've been playing lately, nowadays I don't have much time to play (for example for online clan playing) because of work. But weekends I play more

Thief-series (just bought this recently, oldie but goodie)
Hearts of Iron II (+Doomsday-pack), going to buy HoI III soon
Left4Dead
Tom Clancy's Ghost Recon
Faces of War (cheap and good as hell, highly recommend this)
Football Manager 08
Call of Cthulhu: Dark Corners of the Earth (highly recommend this despite the bugs, also it's quite cheap)
Diablo II
Painkiller (one of the best back-to-basics-FPS games I've played)
Bought, but not started yet:
Rainbow Six: Rogue Spear (have played this through many times, but not with PC)
Rainbow Six: Ravenshield (Also played this many, many times, it was time to actually buy it)
Rainbow Six: Lockdown (got it cheap)
... And others
I usually play only like one game + one side game at a time... I like to focus on few games

Then I change the game. I wish I had more time, there are just awesome games out there to be played...