Between January 1 and December 31, 2009, Microsoft collected data on the most popular Xbox Live games of that year based on unique user connectivity. For the original Xbox, which had been discontinued in 2006, this would be the final year that Microsoft would collect its player statistics for online games, as the console's support for Xbox Live would be discontinued just three months after the data was published in January 2010. The list of the top 20 most popular games goes as follows:

1. Halo 2
2. Star Wars: Battlefront II
3. Fable
4. Counter-Strike
5. Conker: Live & Reloaded
6. Doom 3
7. Tom Clancy's Splinter Cell: Chaos Theory
8. Star Wars: Knights of the Old Republic
9. Star Wars: Battlefront
10. Star Wars: Republic Commando
11. Burnout 3: Takedown
12. Fable: The Lost Chapters
13. Call of Duty 2: Big Red One
14. Call of Duty 3
15. Call of Duty: Finest Hour
16. MechAssault 2: Lone Wolf
17. Crimson Skies: High Road to Revenge
18. Guilty Gear X2 #Reload
19. Tom Clancy's Rainbow Six 3
20. Gauntlet: Seven Sorrows