Major nelson, director of programing for xbox live, recently published this list for the past years gaming titles. Here is what he had to say.

"Here are the top games for 2006, based on Xbox Live connectivity.
The following rankings are based on data collected from 1/1/06 – 12/29/06:"

 2006 Top Xbox 360 Titles (UUs)
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: Battlfrnt 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