I'm certainly not going to dismiss a game out of popularity. I really liked Cod 4 after all. But a failure to innovate does cause stagnation, just as it does in any other medium. At this stage I've been completely burnt out on military shooters. I recently played Crysis 2, a well designed, highly polished shooter, which was far more open than the usual wave of Cod clones. And I still didn't enjoy it half as much as Mirror's Edge.
It wasn't on the principle that it was new, it was the fact that the freshness made me enjoy it more. I'm not basing it on an idealist philosophy where I like it because I should, new shit is just more fun.