Orange box come with the best fps ever made Half life 2 and its expansions (biased opininion I know) Portal, and one of the best Multiplayer games ever made (Team Fortress 2)
It out on PC and 360 now, PS3 later (it will be crap though the port is done by EA)
I highly reccomend you get it for PC because it costs less, you don't have to pay for online, and you can have more players in TF2. Also I hear the xbox version has lag issues.
So yeah get Orange box, 5 games in all
Half life 2 - Great fps, if you think otherwise you play too much halo.
Half life 2 Episode 1
HL2 Ep2
Team fortress 2 - Really awesome multiplayer shooter, I stopped playing Halo 3 because of it.
Portal - Neat little First person puzzle game