Now when the ICO+Shadow of Colossus Collection is out for the PS3, I was wondering that are these games some how related to each other? Is it better to play ICO first or vice versa?
After getting an answer I searched again and found out that Wikipedia has also a small section how these games are connected to each other.
Yes, they are. Shadow of the Colossus is a prequel to ICO, set in the same world. In addition, Shadow of the Colossus explains some of the story from ICO. So I would recommend playing Shadow of the Colossus before starting ICO.