One of the great 360 games. Its more modern and about a war with America vs a fictional Russianterrorist group.
Its basically if you mixed all the modern shooters and burned them, then took Halo 3 and made it have game sex with the whole call of duty series to make a awsome game baby that occurs inbetween the times of each game.
Also you get to stab people, which is always enjoyable.
Person 1: Hey wanna play halo 3?
Person 2: Nah I'm tired of being killed by 5 year olds, so ima play Call of Duty 4.
Person 1: So you wanna play with rednecks and middleaged men?
Person 2: Hells yes, so I can own them with my young people skillz!
The game that made many Halo fans immediately drop playing Halo 3 online for "more realistic" gameplay, in Call of Duty 4. Frequently causes said Halo fans to diss the shit out of it, later crawling back through the doggy door sorrowfully and returning to their beloved Master Chief. Could possibly be replaced by Vegas 2 in terms of Xbox Live fads.