What's innovative about it? Not much. So what? When did innovation become the end-all, be-all of what's fun?
Halo 3 multiplayer is a blast. I'm not under the delusion that it's so absolutely new and different and other games don't have "innovative" multiplayer modes, and I doubt many other people (who aren't extreme fan-boy types) would argue that either.
That's not the point. The point is, it's fun, for reasons Darky went over, as well as others. Saying it's hype is kinda ridiculous. "Yeah, the game had a lot of publicity, that's why I find it fun!" Erm, no. Sorry.
If you don't find it fun, hey, great, play something else. Why spend your time worrying about why other people find it fun?