I'm guessing those that were thought to be good and not one you acknowledge as good but just didn't get into. Quite a difference.
My most prominent one was Gears of War 1. The game was a very shallow shooter that didn't even have some of the things that had become a necessity for most shooters. Its like you play a game like Half Life 2 and you look at Gears of War 1 and its like it's ugly sister. I thought the game was decent but it was not a great game. Gears of War 2 on the other hand is shaping up a lot better.
Fable 1- another game I just couldn't get into. Although I do acknowledge it as being a good game but just couldn't stay with it.
Elder Scrolls: Morrowind- same as Fable 1... but this one just took way to long to get to anything. Was like playing a hollow shell that where the light of the end of the tunnel was simply another shell to enter.
Metroid Prime- similar reasonings to Elder Scrolls that it just didn't get anywhere fast enough for me.
That's it for me right now but I think eventually I'll be adding Littlebigplanet to this list.