Ico

Ico is just simply magnificent and it is far better then Shadow of the Colossus. Shadow had a moral dilemma as it's central story... to rescuse the girl he loves, the guy has to kill all these beautiful, innocent and generally harmless creatures: A selfish act if there ever was one.

Ico is more about the innocence of friendship and... bahhh, there's a great storyline guide you can get off gamefaqs to tell you more. I think Ico is just a much more atmospheric and compelling game then Shadow. It's fantastic and you should play it as soon as you can if you haven't already done so.

SotC had the better soundtrack and I loved both games. The thing with shadow was, he had to kill the 16 colossi to bring back the soul of the one he loved, not caring what happened to him. Wanderer was pretty much selfless. ICO was amazing.