I really do not mind if there is multiplayer I even prefer to have it then to not have it in most FPS games, but in others I don't think it should be there, ie: Mass Effect 3. I do believe that multiplayer should be focused on by another studio or a separate smaller team, because like you said Rob about Max Payne 3 "unlike most games, SP came first in that game, not second, and it shows." and I totally agree.
I think many COD and BF games have suffered both in SP and other critical development areas (like the BF2 engine) because they focused primarily on MP and even though they have had moderate to amazing success from title to title. I think it sends a bad message to other studios that it's only thing gamers want, when it isn't.
In my opinion I seriously think Mass Effect 3's multiplayer was developed so they could sell more key codes for that $10 fee because so many people bought ME2 used and didn't care about the DLC that came with it.