Activision's hit shooter Modern Warfare 2 reportedly brought in over $500 million worldwide in just its first five days. Now the Infinity Ward-developed game has generated over $ billion in sell-through revenue worldwide since its launch just over two months ago.

The numbers, which come from internal estimates from the publisher, show that the game has truly achieved mainstream popularity. In fact, games like Mass Effect 2, an RPG, are aiming to go after the big Modern Warfare 2 crowd by improving the in-game shooting combat features. Kotaku quotes BioWare's Casey Hudson as saying, "We need to put Mass Effect 2 combat against the very best that is out there. And say this is absolutely state of the art shooting. I think in combat moments they will feel it is the same sort of game."