For myself, in recent years it would have to be a fight between Gears of War 2 or Halo 3.
Now don't get me wrong, I love Halo 3, (despite it's crappy ending. GoW2, however, can go DIAF), but I have never seen a game violate it's own rules so quickly. Example:
Throw gernade at guy. Gernade explodes. Guy dies. Now go try it else where. Well, that didn't work, did it? (or, has this one ever happened to you?) Fire your BR at someone eight times in the head, and they still don't die, yet they fire at you twice and you die? Wtf? I thought hitting someone in the head took longer than that to kill? 'Nope, just with your weapon.' What? Why? 'No reason.'
Now, I only have two problems with GoW2; you press A (xbox360 controls) to do everything, and the chainsaw won't cut everyone. Why? 'because that guy is to big!' Oh, really? So the chainsaw that can cut people my same size in half in a matter of seconds won't even leave a gash on someone else? 'Nope.' Will you at least try? 'Nope'. Gah!!
So yeah, something like that.
Edit: Ah, I totally forgot all about the Destroy all Humans series. Bad controls, horrible voice choices (not bad voice acting mind you, it just didn't fit the characters for me), and poor graphics. I mean, the last one came out on the 360, why does it look like a PS1 game?