IIIIITHE1IIIII on 24 November 2012
For a $500 PC you should be able to play both first Halo games, if you haven't already!
If it's slower than that, I'd recommend Quake III Arena. It doesn't have a deep story or anything, but it's some awesome fast paced multiplayer against bots/online players which definitely covers up for it.
Some more basic suggestions would be the GTA - and Counter-Strike games. Old but Gold :)
