To be perfectly fair, Call of Duty lifted more from Medal of Honor: Allied Assault, which the people who formed Infinity Ward released 9 months before Battlefield 1942 came out. For that matter, implying that a largely single player game focused on providing an adrenaline rush of a single player experience ripped off an objective based multiplayer game with huge maps and a focus on vehicle combat is a laugh and a half. The two are nothing alike outside of their setting.
Same goes for Battlefield 2 and COD4. The setting is similar, but the games are radically different from the very focus of their gameplay to how they feel.