Its only real flaw is the length of gameplay
Both Ico and SotC are puzzle-based adventure games. In Ico, instead of trying to figure out how to slay the beasts, you are supposed to figure out how to work contraptions inside the castle, while at the same time protecting a girl and never letting her out of your sight.
The main challenge of the game is to fight off hords of shadows while making sure the girl is not taken by them. Once that happens, it's game over. The girl is useless at fighting, and so helpless that she can't even defend herself. The only way to keep her safe is to hold her hand at all times, unless you need to say fight or jump or climb ladders. There was something about the simple act of running together holding hands that really appealed to me.
I initially bought the game because I wanted a puzzle-filled game, and after finishing it, I was pleasantly surprised. The overall music is beautiful, and so is the ending. The camera isn't the best around, but it certainly does not get in the way of gameplay. And the only thing preventing this game from getting a 10 is the length. You can easily finish this in less than 10 hours, and there are no side-quests for NTSC version.
This is one of those games that is like a work of art. Just experiencing the game is worth the time.