Playing "Ico" is kind of a Zen-like experience, but it isn't dull. I bought it after overhearing one young guy complain to another that it didn't have enough combat. So I was surprised at how often I had to stay aggressive to keep shadow demons at bay.
I don't understand why "Ico" is in the mark-down bin at so many stores, especially as it consistently earns such high praise. Even the New York Times gave it a good review! I suppose it appeals mostly to adults --like me-- who can appreciate how special it is. It might lack appeal for you if you're the kind of person who can't stand to be in nature without your cell phone or your .mp3 player.
There is great pleasure to be had just in padding around the environment. The ambient sound gives one the feeling of being immersed in a vast world. There is something wistful about the ancient machinery, the plaintive cry of the hero (delightfully, you can make him call out as often as you like by pressing a button), the misty backgrounds....
Meanwhile, for me, "Ico" has just the right amount of fighting (not too much) and puzzles (hard, but not insanity-making). The only drawback is a sense of repetition in the gameplay, which is a flaw in such a short game. Still, just writing about it makes me want to play again.