Really, all I can recommend to you is the tons of multiplatform games that are available on Xbox360, PlayStation 3 and PC, and a couple of games that I recall seeing as available for PC:
Left4Dead is a good series I suppose.
StarCraft 2 is pretty amazing.
Diablo 3 is going to be released in the near future and that will be a great buy, I'm already sure.
Guild Wars, though an MMO, is still freaking amazing.
World of Warcraft is an MMO as well but that game's reception is over the top. I believe a certain moderator on ZD has a history with WoW.
Star Wars The Old Republic has a good deal of hype but is also an MMO.
IF you can get your hands on Star Wars:Knights of the Old Republic [KOTOR, not SWTOR], I believe you will have played a legendary game.