New Game - FPS

Ok, I'm looking at BF2, Black Hawk Down, or something else that grabs my attention. As you can tell, these titles are old and cheap, I'm short on cash from my 360 and some accessories and am going out tonight to pick up a game. May even consider Counter Strike. Oh and it needs to be FPS.

I've played BHD on PC and loved it, single player was wicked and multi player was perfect. So I'm considering getting it for 360. Also, I need the single player to be lengthy and replayable. I know Counter Strike is great for that, you can play that all the time and the bots never get old.

So what one should I get? Or is there something else cheap and fun?

I've played all the Splinter Cells on my old GameCube.

And CoD2 is a little too pricey for me right now (cmon summer... cash time). And lolz, I tried the F.E.A.R. demo at like 1:30am with the lights out and couldn't do it... damn little girl freaked me out giggling and stuff :D

I guess I could try BF2, what's the single player like?