Gotta be Halo. It probably wouldn't be fair to say I hate it, it's a perfectly ok FPS. That's just it though, it's just another generic shooter and it has almost as much undeserved hype surrounding it than Christianity. Sure, LAN matches with friends are fun, the same can be said for pretty much any other game in the genre.
GTAIV. Don't get me wrong, I adore the series, particularly San Andreas. However, they really seemed to fuck it up with the jump to the next generation consoles. They actually cut down on the available selection of vehicles and guns, made the height ceiling for aircraft lower than the buildings (I fucking HATE that so much I cannot begin to describe it), restricted you to only a city environment, added a bunch of fluff (in-game TV and internet) nobody would ever look at unless they were bored with the main game (something you'd think the developers were trying to avoid), reduced the customisabiltiy of your character to nigh-on nothing and for all that all they did was pretty up the graphics (seems to be a running theme with this generation of games, no?). Ah well, at least we have Saints Row II. They did far better job of things I must say.
Finally, a retro title that I cannot stand. Crash Bandicoot. It's just so fucking boring, tedious and repetitive. Granted, the newer titles try to make the gameplay a little more varied, but it's stil ass.