The next time anyone boots up MW2 look at one of the screens right around the title screen. I am pretty sure the COD series uses this engine as well.
They use a modified id tech 3 called IW 4.0. It's not hard to find this info, you don't need to load a game. You're already on the internet.
*edit - Not flaming. Misinformation gets spread constantly, despite resources being constantly present.
