*Jumps on the bandwagon* Assassins Creed for me, not because of the repetitive gameplay because all games are like that if you break them down. But because they didn't offer anything like the initial concept, of being able to plan your attacks, using stealth or brute force and then escaping away using the crowd to your advantage.
All the "bosses" where setup with no planning at all. Then it was simple few button presses then run for it.
Can't believe some people are saying Halo 3 as well, if you expected anything different to what was delivered, its your own fault for falling for the mainstream hype machine.