Major Nelson has posted the list of the top played game on Xbox Live for 2006. One mild surprise is that despite only being available the last month and a half of the year, Gears of War was the top game for Xbox 360 played on live. Other tops were UNO for Xbox live Arcade and Halo 2 for the original Xbox. One caveat is that multiple Gamertags can play the same purchased copy of a XBLA game, so the order may be funky due to this.

The complete list:

2006 Top Xbox 360 Titles (UU's)
1 Gears of War
2 Hexic HD
3 Call of Duty 2
4 Ghost Recon 3
5 Oblivion
6 PGR3
7 Perfect Dark Zero
8 Call Of Duty 3
9 UNO
10 EA SPORTS Fight Night Round 3
11 Saints Row
12 Geometry Wars Evolved
13 DEAD OR ALIVE 4
14 Texas Hold 'em
15 Madden NFL 07
16 DEAD RISING
17 Need for Speed Most Wanted
18 Tom Clancy's Rainbow Six Vegas
19 BFMC
20 Splinter Cell Double Agent

2006 Top Arcade Titles (Purchased)
1 UNO
2 Street Fighter II' Hyper Fighting
3 Geometry Wars Evolved
4 Marble Blast Ultra
5 PAC-MAN
6 DOOM
7 Ultimate Mortal Kombat 3
8 GALAGA
9 Gauntlet
10 Frogger
11 Bankshot Billiards 2
12 SmashTV
13 Contra
14 Zuma
15 Texas Hold 'em
16 Bejeweled 2
17 Feeding Frenzy
18 Small Arms
19 Cloning Clyde
20 LUMINES LIVE!

2006 Top Original Xbox Titles
1 Halo 2
2 Battlefield 2: MC
3 Star Wars: Battlefront 2
4 Madden NFL 2006
5 Counter-Strike
6 Splinter Cell Chaos
7 Forza Motorsport
8 Call of Duty 2
9 Ghost Recon 2
10 PGR 2
11 Rainbow Six 3
12 NFS Most Wanted
13 Ghost Recon 2: SS
14 Rainbow Six 3 BA
15 Ghost Recon AW
16 Far Cry Instincts
17 Madden NFL 07
18 Conker: Live Reloaded
19 Tony Hawk Am Wasteland
20 RS 4: Lockdown