Monkey Island IV
As much as I stick to my guns that MI 1-3 were created while the coders drank nectar from the gods, I must concede that MI4 was dismal. The whole 3d look and movement was terribad.
Duke Nukem Forever should be added to this list to the likes of Doom3.
Prince of Persia 2 (yes the old one) was also a poor reminder of the epic original title. It left me hanging - and not in the good way.
As for even mentioning KOTOR II in this article, makes me want to curse you with the fleas of a thousand camels! semi-jk! Obsidian did a fine job, but the ending was completely rushed by the bean counters. KOTOR II had an amazing soundtrack and is still my favourite RPG to date.