Super Mario Galaxy 2
I really don't like that game. Every other Mario game I've played, I've enjoyed, though SMG also to a lesser extent than the others. There are just too few things about it that don't bug me. Everything from the music, sound effects, power-ups, bad Yoshi controls, to the aggravating gimmick levels and overall level design. It just puts me in a bad mood.
Also... I feel obligated to say Suikoden IV since it's my favorite series, but I still find the game enjoyable enough in its own right.
Castlevania: Lords of Shadow
I don't know if this one is fair to call out since I have a difficult time really believing it's a Castlevania game for all the reasons everybody already knows. I should have known I wasn't going to like this game since I don't care for the style of gameplay, but I gave it a chance anyway. What madness drove me to play it through to completion, I may never know.
I'm surprised by the mention of Paper Mario. I really like that game. Actually, I tend to tout it as the best game on Wii and one of the very few Wii games worth owning.
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"Filthy lawbreaker, unhand that vending machine!" - Casey Jones