lately, ive been more into quick, casual gaming, arcade games you could say - something that doesn't require alot of time & commitment. Team Fortress 2, Counter Strike: Source, Colin Mcrae Dirt, Unreal Tournament 3; are the PC Titles i play atm.
my Wii games would also fit nicely into this catagory.
Where'as previously, i was a fan of games (for PC) such as Oblivion, Supreme Commander (+FA), WOW (i still play WOW, just usually not for long.) Flight Sim X. HL2 + Episodes...
So really, its all personal preference, and what your rig is capable of running. (but if your rig is a serious limiting factor, i recommend spending that money on upgrades. not games