Xbox 360 Top Live Games
1 Ghost Recon 3
2 Call of Duty 2
3 Oblivion
4 BFMC
5 Final Fantasy XI
6 EA SPORTS™ Fight Night Round 3
7 2006 FIFA World Cup
8 PGR3
9 Perfect Dark Zero
10 dead or alive 4

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

If the lists were combined, Halo 2 would be ranked first, followed by all the 360 games.

Informaion comes straigiht from Major Nelson's blog.