CaptainCrunch it depends on a few things
1. Like multiplayer ?
Go for halo
2. Like awsome storytelling?
go for bioshock
3. Like 1+2 go for orangebox.
I havnt played orangebox on my xbox however i do have it for my computer i play it nearley everyday. It has 20+hours of singleplayer gameplay in halflife 2. Portal owns and TF2 will blow your mind.
Halo is awsome online with alot of replayability and a great varity. The only thing is there are spamming n00bs(children) who have sex with their mic..
Bioshock is the best if you dont have XBL because of its nice and big storymode. (also satisfying)
they are all awsome games.
I reccoment Orange box though