In COD4 you play as 3 main characters, depending on the mission and where and ever what year you will be that character. You switch between Missions as either S.A.S or U.S.M.C.
This Game has great graphics and uses the enviorment extremely well, depending on where you decide to take cover depends on if you live or die, and trust me most the time you go behind a car that just may explode on you when you least expect it. All in all COD 4 made me very very happy and I cant stop playing. And on my classic 1-10 scale COD4 gets a 10.
The multiplayer is the best part of call of duty 4. Since the single player is short you will spend most of your time on multiplayer, And because of all the the things that go together to make a great multiplayer experiance that are in Call of duty 4, The multiplayer is the greatest part of Call of duty.