Straight from Major Nelson's blog, it's the Xbox Live Activity list for the week of 11/27.
Xbox 360 Top Live Titles (UU's)
1 Gears of War
2 Call Of Duty 3
3 Small Arms
4 LOST PLANET OnlineDemo
5 SUPERMAN DEMO
6 Madden NFL 07
7 Tom Clancy's Rainbow Six Vegas
8 Rainbow Six Vegas Multi Player Demo
9 Call of Duty 2
10 Oblivion
Top Arcade Titles (Full Versions)
1 Small Arms
2 UNO
3 Contra
4 Ultimate Mortal Kombat 3
5 Street Fighter II' Hyper Fighting
6 geometry Wars Evolved
7 Texas Hold 'em
8 DOOM
9 PAC-MAN
10 Defender
Original Xbox Top Live Games
1 Halo 2
2 Battlefield 2: MC
3 Madden NFL 07
4 Star Wars: Battlfront 2
5 Counter-Strike
6 Forza Motorsport
7 Call of Duty 2
8 Call of Duty 3
9 Ghost Recon 2
10 Rainbow Six 3
My favorite game on the list is Small Arms. Sure, it's a blatant Smash Bros rip off….but who cares? It's definitely the best game on the Marketplace right now.