Crimson Skies is, IMHO, the best on the service. Mech Assault has so much downloadable content (Some of it paid at $4.99.) that it's nearly a diffferent game online from when you bought it. Return to Castle Wolfenstein was the most played game a year ago and the Beach Invasion level was bout the only thing I played for three months.
ESPN 2K5 is going to have tons of gamers. If you're just a casual sports player like me though chances are you are going to be a whipping boy every time you game online. There are some excellent players I've come across.
PGR 2 is phenomenal online and even the offline Live stuff like downloading ghosts, knowing where you rank in the world etc. are just incredible. I don't have RSC 2 but I assume from what I've heard it's just as great.
CounterStrike? This is the one Live game everyone loves that I can't get into. I've tried several times but it does nothing for me YMMV.
Midtown Madness 3, again, hated this game, couldn't get into it yet some love it. I fell in love with Midnight Club 2 online last summer and had a blast with it, I don't know how many people are still playing it though.
Liitle gem that no one's mentioned that my GF and I have actually had fun with is Tetris Worlds. I've actually met some nice people on there and had real conversations so in that regards it's like XBL's "parlor" game to me. It also has custom soundtracks. Yeah, it got bad reviews but I have no idea why, I mean... it's Tetris with a different wrapper and online play. How can that be bad?
Well that's the long and short of it as you can tell the consenus on what the good games are is very consistent. There are no major disputes as to what's good on the service.
Oh and Rainbow Six 3 is THE online shooter. I have XIII as well but the online part was obviously an afterthought and isn't that entertaining.
