Well I'd personally go put my money towards a Co-Op game like the new Army of Two because when I play games its with friends. If it wasn't for friends on xbl I wouldn't play...hell if it wasn't for friends I wouldn't be gaming.
It depends playstyle to playstyle. I found MW2 to be more of a game for run & gun with plenty of fun and memorable moments. I also found BC2 to be fun as well because I play it online with friends as well but it's more realistic.
Part of my next check I get is going to go towards Ao2 the new one, full pre-order on Reach along with some laptop **** cause I can't stand it w/o a wireless keyboard and mouse o.o Other than those games nothing else co-op comes to mind!
Honestly man, i think you should get Call of Duty Modern Warfare 2, especially if you're already set up with xbox live, it's probably the funnest and most time consuming game out even though its like what almost a year and a half old now. Its probably the only thing I've had in my xbox since I bought the game.