What are all the popular PC games

Was just looking at the steam selection, just got the client am more of a ps3 gamer. anyway, what are the best games out


I like the look of gary's mod and chivalry looks really good but i wouldn't drop that much on it, ill get it when its $10 

Crysis series. 

Team Fortress 2 is free and loads of fun

DC Universe Online is too.

Battlefield 3.

I can't think of anything else right now

Natural selection 2

Get Valve and early ID games, they're all good.