Straight from Major Nelson's Blog....

Xbox 360 Top Live Games
1 Call of Duty 2
2 Madden NFL 07
3 Texas Hold 'em
4 Ghost Recon 3
5 DEAD RISING
6 Chromehounds
7 Oblivion
8 BFMC
9 final fantasy XI
10 NCAA 07

Original Xbox Top Live Games
1 Halo 2
2 Battlefield 2: MC
3 Madden NFL 07
4 Splinter Cell Chaos
5 Counter-Strike
6 Pro Evolution Soccer 5
7 Rainbow Six 3 BA
8 Star Wars: Battlfrnt 2
9 Forza Motorsport
10 Madden NFL 2006

As always....If these two lists were combined, Halo 2 would be first, followed by all of the Xbox 360 titles.