Call of Duty was the Halo killer. It got such a online recognition that it topped Halo 3 online usage for quite awhile, and it also outsold Halo 3 (PS3/360 combined sales) something that a lot of people thought would never happen.
Halo is still the single console FPS king when it comes to sales, but gameplay wise a lot of people chose Call of Duty MW over Halo 3.
It's just that simple.







