I don't think people moan enough when games are too much like the last one. Take a look at games like Grand Theft Auto and Halo, neither of which have really changed since the beginning of the last generation. That doesn't stop them from selling retarded numbers of copies.
But they definitely moan too much when games change. When Final Fantasy Tactics came out, people were saying things like, "White Mages don't cast Protect any more, Green Mages do! BAAAAWWW!" and "I can't spam Ultima at everything from the beginning of the battle! HOW WILL I EVER BE CHEAP NOW!" They can't tell the difference between drops in quality and changes. Idiots.