Definitley a must have!
First of all i'd like to clear a couple things up that i saw with some other reviews. Yes, the campaign is short but it will blow you away with the intensity of war and replay value is very high because as you raise the difficulty it becomes more and more realisic. Second, someone mentioned that your players dont have names. Let me clerify this, as a marine you will be Sgt. Jackson and as SAS you will be "Soap" MacTavish. Finally during the nuclear impact seen "which was one of the best explosions ever scene on a game" it confirms that Jackson is dead before you go to the next map.
Alright now i feel better, anyway if you dont already have call of duty 4, buy it, you will not regret it. The only problem I saw with this game was the length of the campaign, however the intensity of it definitley made up for it.