Believe it or not, just because it's a shooter doesn't mean the game is the same each time. The gameplay of CoD4 is completely different than MW2. Black Ops is made by a completely different company, and I think it's hard to argue that CoD5 was a copy of CoD4 (also it was made by Treyarch). Even if you can't acknowledge that there are differences in each game (like I dunno, a completely different single player story, entirely new multiplayer maps, new guns, etc. etc.) I don't know why you would call it a scam, and not just Treyarch and Infinity Ward finding a formula for making a game that will sell.
Also, why the hell aren't you bitching about Madden? There have been 17 goddamn Madden games (18 at the end of the month) released each year since 1994, with tweaks that would be considered updates in other games, but are released as a new game each year. It's not a scam, but come on, there have been three modern warfare games. Three.
Also, I'm not a Call of Duty fanboy. I don't give a stuff, I just have no tolerance for people making handicapped arguments and I'm in a bad mood.