My least favorite game that I purchased would have to be...
Shadow of the Colossus.
For as much hype as SotC got, I hate it. The controls are awful. It feels like you're moving through sludge and the jumps are so hard to control. On my way to a Colossus I remember trying to jump over a hole in a bridge and falling down, down into the water far below again and again and again. To me, the controls feel sluggish and sloppy.
Then there is the gameplay. No real challenge, just frustration. You climb on the first Colossus, for example, and as he flails around you have to sit and wait before you can do anything. Done flailing? Hooray now I can continue slowly climbing. Crap, flailing again. Oops, ran out of stamina, guess I have to do the whole thing over again. At least I'll never die. It's a grand test of patience. And don't get me STARTED on the final Colossus... or the little bull-like one where you have to use the torch.
So you argue the difficulty is less about skill and more about the puzzle aspect. Maybe it's the fact that I've never played a real puzzle game, but to me, puzzles should be something that you have some idea what you're supposed to do, you just have to put the pieces together to figure it out. Msybe I was just in a super-dumbass mood when I played SotC, but for many a Colossus I wandered around the arena not understanding what I could possibly do. Oh, so when the Colossus swings at me and I'm near the edge of the area, it pushes up a walkway to another level? How was I supposed to know that part of the environment could be interacted with??
For a game to be one of my absolute favorites, it needs replayability... or length. There's nothing I love more than sinking hours upon hours into a great game... upgrading all your weapons in Ratchet & Clank UYA, getting the stealth camo in MGS3, beating all difficulties in DMC3, getting 100% in Okami... I love it all. SotC is a short game to begin with, and since it's "puzzle" focused, the "difficulty" is nonexistent (well, the frustration is still there, I suppose). I know this is more of a personal complaint, but it bothers me anyway.
Then after I became super frustrated with it, little things started to bother me, too. The framerate issues. The annoyance of trying to up your stats by hunting geckos. The poor map.
I kind of understand why people love this game. The Colossi are awesome, it's a really unique game idea, and the minimalist story was intriguing and motivating. I wish I loved SotC like everyone else, I really do, but I can't.
/rant.