Ico is one of the few games that, every year or so, I pop it in for a playthrough.
T o me, I love the castle, I love the puzzles. I thought the fighting was good enough (a weaker portion of the game). I thought it was everything that Tomb Raider should have evolved into at the time.
In fairness, I don't think it's overrated. This is a 8 year old game (came out in 2001). So, obviously, if you have no experience with the game, the graphics won't wow you like they would have. Also, many of the things that were new with it don't feel as new anymore (it's like watching the Matrix now for the first time and saying, well, the slow mo bullet is so boring now. True, but it wasn't when they invented it).
Personally, I think it's a great game, and it'll forever be a part of my collection. I would say give it a try if you are looking for the adventure/puzzle of a game. But, try to remember what graphics were 7 years ago, so you aren't comparing it to games that came out years later.