Ah, the 'elite' pc gamer jerk circle ... just kidding ... but go for those unique and pc-only games that are really worth your money, and time.
Strategy games:
Sins of a solar empire - This is a hybrid game, mixing 4X (eXplore/eXpand/eXploit/eXterminate) and RTS (real-time strategy)
Company of Heroes - This one too can fall into the hybrid category, with RTS and Tactics genre involved
World in Conflict - More tactics than RTS.
RPG
For Action-RPGs:
Titan-Quest Bundled Pack
For cRPGs:
Neverwinter Nights 2 + Expansion packs
P2P MMOs
1. Warhammer Online - If you want those massive battles with 100 of players charging at you with nothing more than their spell books, while you poke them with your puny dagger of penetration, this game is for you.
2. World of Warcraft - Give the trial version a try, and judge for yourself whether people who hate this game are in the right.
Action games and FPS
The Orange Box - nuff said