Ok, SotC beat. Funny, the hardest boss was #15 for me. I had to fight him for an hour since I couldn't remember how to get him to drop his sword, and then I had trouble getting down to his palm for the final stab. I wish you could turn of Mr Hint Voice. The 20th time he tells you the same unhelpful hint you wish you could stab sound.
Edit: Thinking back, I remember Ico more fondly. Shadow of the Colossus was impressive to me for its unconventional design, like Ico, and the battles with the colossi were incredible but in between those battles there wasn't much fun to be had. Sure, there was the wonder of the world and a slight element of exploration, but it was kind of boring. Ico had far fewer lulls and when it did, there was still a large sense of weight to the game.
I was thinking about the emptiness of the SotC world and how I really enjoy the minimalism. They built this huge land and you only really need a few sections of it. The rest is just there for you to enjoy and explore.
If the game was made by anyone else they would have filled that space with lots of little bad guys to fight so you can earn XP, level up your grip and health, have you find 30 variations on the sword and bow, etc. The simplicity is just refreshing. You don't even have to go "earn" the sword or bow, you just have them from the very beginning. You never come to a colossus and go "Oh I need <special magic widget> to beat this guy."