I thought I'd absolutely love Ocarina of Time. "Greatest game ever" and all that. Was expeting a 9-10 game, I got a 6. Maaaaybe 7. Also, Twinsen's Odyssey (aka LittleBigAdventure 2) is one of my favorite games ever. I played the first game and quit after 10 or 20 minutes. I should go back though, with a different mindset this time.
Shadow of the Colossus is awesome! Ico is not, as much as I wanted it to be. Mediocre at best. I was also expecting more from FFVI, but it's one of my least favorite of the series. Folklore looked pretty awesome, and I had a great first impression. Then it just nosedives into repetition (you basically play the same levels and bosses twice).

FFVIII's Draw system always pissed me off, but when I finally beat the game, I discovered the game actually gets pretty fun from exploiting the broken mechanics.

Other than that, all I can think of are games that I thought would be decent/good, but turned out great/excellent (Call of Juarez Bound in Blood, Lara Croft and the Guardian of Light, Rochard, ActRaiser, Half-Minute Hero, Daxter, I could go on and on).

Thought I'd love:
-The Last of Us
-FF 13 (all three of them)
-LA Noire
-Gears of War: Judgement
-Dead Rising 2
-Killzone 3
-Xenoblade Chronicles


Thought I'd hate:
-Magna Carta 2
-Endless Ocean
-Wii Play
-Dance Central
-Resistance Burning Skies
-Bionic Commando

Bioshock. Thought I'd love it. Wanted to love it. Couldn't even be bothered to finish it.

I don't play games I think I'll hate.

Thought I would hate Mass Effect because of YET another shooter. Couldn't put the game or series down.

Thought I would love Dragon Age 2, got bored real quick.

i thought i would like ocarina of time, though i would hate Singularity

Thought I'd love but didn't:
Bioshock
Red Dead Redemption
Heavy Rain
The Last of Us

Thought I won't like, but I did:
Bioshock: Infinite
Beyond: Two Souls
Uncharted: Golden Abyss

I thought I would love Drakengard 3 but nope and I thought I would hate MW2 but nope

Interesting response!

I thought I would like Metal Gear: Twin Snakes (Twin Snacks) but was disappointed.

I thought I wouldn't like Tetris till I actually played it. Almost hooked!

Hate but thought I'd love: Everything Elder Scrolls

Love but thought I'd hate: Ratchet & Clank series

I remember being so excited to play Morrowind and how disappointed I was when I first played it. Now I give every Elder Scrolls title a shot hoping I'll like one. I... have not.

When I first laid eyes on Ratchet & Clank on the cover of a OPM magazine my thought was God that looks stupid! It now stands as one of my favorite series.