I think there's more room for funny zombie games, especially if they make use of zombie animals rather than just humans.
I think there's room for both extremes really, animalistic zombies, and zombies that are basically people shuffling around. It's the middle ground that people seem to be getting sick of, where you have some special zombies, and most just shuffle around.
Specifically, games that have well thought out stories (or at least "deep" survival stories) seem to be doing well with zombies right now.
Personally i think the zombies are irrelevant.
What makes the game fun ? L4D for example is not fun because of the zombies, its fun because of how its mechanics push people to cooperate, You could take that game and move it to a sci-fi setting with aliens and it would still work.