At the core all games in their respective genre are pretty much the same. I don't expect innovation from mmo's because it's rare and hard to come by, and in my opinion same with other genre's. Though I would guess sandbox element has become more of a factor. I mean in my experience in CoD: MW2, after playing the game for a while it is actually boring. It's nothing new just a better well made FPS at the time. Though once xbox 360 modders got a hold on the game it open a whole new level of entertainment. I play that game for a straight year. I normally don't stick to FPS for more than a month at most but when modded lobby's came out there was so much more varieties to the game.
Though the problem is a lot of companies, developers, and publisher's make a lot of mmorpg that is literally nothing much different from one to the next. Console games tend towards more to story aspect of gamers. You wouldn't exactly play games like Sleeping Dogs thousands of hours if the next game had pretty much the same story and style and the game was practically the same.
edit: Really what just reminded me when I typed that out was that it would be really interesting if mmorpg were more tended towards story's instead of the world itself. I mean I really liked how The Secret World had a lot of episodic like story content. Along with well thought out investigation quests.