Ico is lesser known/underrated because it's the spitirual "prequel" to shadow of the colossus. The game first released on PS2, but you can play it on PS3 from The Ico & Shadow of the Colossus Collection which is a HD version of both games on a single disc.

I played the PS3 version on RPSC3 and it worked flawlessly except for a few crashes.

The game is an experience unlike any other. Sometimes we say about some games "they don't hold your hand", like the Souls game. Well, this game will never give you a single hint, it's that mantra pushed to the extreme. It's best described as Portal without the portals. It makes the experience very immersive since there are no HUD elements, no voice telling you to do anything. It's essentially a puzzle game, but it won't feel like a puzzle game, it will feel like an adventure you are solely responsible for and for which the end result will be 100% your achievement; It's not a multiple endings game, but it's such a well designed game that the player will feel proud of the journey.

I can't say much more without spoiling, all I can say is please give this game a shot, it will change your perspective on games as a whole.

My rating, 10/10. There are 0 flaws with this game, not a single con I can nitpick about. There's barely any dialogue but it can easily make you quite emotional.