Well, for this week at least. Major Nelson has released the most popular games on Xbox Live for last week, and the number one slot, for the first time in just about forever, isn't Halo 3. It's Call of Duty 4. Here is the entire list: 

Call of Duty 4 Halo 3 Guitar Hero III Gears of War Rock Band Madden NFL 08 Assassin's Creed Mass Effect FIFA 08 Forza Motorsport 2

Call of Duty 4 may be a piracy risk on the PC, but it's doing gangbusters on consoles. It's one thing to be really, really popular; it's quite another to unseat Halo-frickin-3.

Infinity Ward? Achievement unlocked.