COD:MW really started the current trend of "realistic" type military shooters on the console (since Battlefield and Counter-Strike had the PC market wrapped up already), although the health system(s) that either allow you to regenerate like you're Weapon X or magic life canteens don't really add anything to the realism, but I digress.
When you get a game that sells really well like that there is a kind of rush to try to copy the game mechanics or try to capture the feel of that particular game. The really stupid thing is that the market quickly gets saturated with theme "me too" type of products, which eventually lessens the impact of the original product. When this happens the next big idea for the genre will begin to take hold, usually as a reaction to the current norm. This is why I think there is so much anticipation for Bulletstorm right now.
So to answer your question, no, COD didn't kill FPS. They just happen to sit comfortably near the top for now.
When you get a game that sells really well like that there is a kind of rush to try to copy the game mechanics or try to capture the feel of that particular game. The really stupid thing is that the market quickly gets saturated with theme "me too" type of products, which eventually lessens the impact of the original product. When this happens the next big idea for the genre will begin to take hold, usually as a reaction to the current norm. This is why I think there is so much anticipation for Bulletstorm right now.
So to answer your question, no, COD didn't kill FPS. They just happen to sit comfortably near the top for now.