I don't know why but a lot of people knock Crysis. I know it's a bitch to run and it doesn't have a constant framerate but I think they gameplay is really fun. Most people that I hear have a main complaint for gameplay of it being really hard to kill enemies because they almost never die unless you get headshots. But that just makes it more difficult.
You can get Crysis, Crysis Warhead, and some other multiplayer thing for Crysis in one $30 pack called Crysis Maximum Edition if you want a good value.
If you want an older game Fable TLC is only $20 and it's a really fun game. If you've played the second one the first one is a lot better trust me. When I heard Fable II was coming out I went and picked up Fable for PC because I didn't own it for xbox but borrowed it and wanted to become familiar with it again and I fell back in love with it. I still play it from time to time.