Grab ESPN NFL 2k5 before all you can play is Madden.
Yeah, get a copy of 2k5. It's excellent, and I normally don't even bother with the football games.
I'd also recommend Ghost Recon 2 if it catches your fancy at all. I've had some really great games on Live with that.
Other than those two and Halo 2, the only other live games I own are Burnout 3, DOA Ultimate, and Links 2004. All of them are great, though they're kind of niche titles.