Best First-Person Shooter ever!
The storyline is excellent as well as, it places you in the role of two soldiers, one working for the US Marines ,whose job it is to help to bring in a middle eastern extremist and the other, a newly recruited SAS soldier who has to prevent the start of a nuclear war. Both campaigns interchange as the story runs out on a single time-line and both are enjoyable to play, however it would have been better if they were a bit longer but you cant ask for the world can you.
Multiplayer is as good as it gets with more than enough game types. It also contains a leveling up system with unlockable guns and perks and paint jobs which will keep you playing all the way to level 55 an beyond.
COD4 is one of the greatest FPS ever and i recommend it to anyone.