Very often, in hyped games.
Metroid: Other M, I thought it was gonna revolutionize Metroid.
SMG2: I said it was the best Wii game, and I cannot replay it again without getting bored in 3 minutes.

I think those were the most notable ones.

never. if i take the time to finish a game is beacuase i really like it.otherwise i'll just stop playing and will never finish it

I agree

Yeah it's happened to me on more than 1 separate occasion.

Bioshock is another big one, what the fuck Mr. Levine?You develop one of the greatest games of all time, but you somehow forget how to pace and write a game for the last hour. I didn't mind in my first play-through, but the second play-through did affect the memories I had of the game.