I don't think developers should pay much attention to their fans. They should simply make a game that they are happy with and then release it. Movie directors don't ask for what their fans want, neither do musicians and artists, video games shouldn't be any different.
And of course I understand that money is a key driver in what IW and Treyarch do. I'm talking about in a perfect world where they are making games because they love games, and want to create something special.