I recently got my hands on a copy of Shadow of the Colossus for the first time a few days ago, and it has completely blown me away. Shadow of the Colossus provides only one major gameplay experience: fighting giant monsters by climbing onto their backs and stabbing weak points. However, by focusing on polishing that one gameplay element to perfection, the developers have created a real masterpiece of a game. From beginning to end, one of the fights against a Colossus reveals the tremendous amount of effort that has been put into making that one experience enjoyable.
I have fought and defeated six Colossi so far in the game, but I am still impressed by the size of the monsters every time. Intellectually, I realize that most of them are all about the same size, but I am somehow fooled into thinking each one is bigger than the previous one. Part of this effect is probably due to how hard it is to see the entire body of a Colossus at once. As long as you are reasonably close to one, its entire body will not fit into the screen. If you are far enough away to see the entire body of the Colossus, then it is easy to be surprised at how much bigger it looks when it finally draws close. Furthermore, the game's camera is usually around the same height off the ground as the hero is when the hero is standing on the ground. So, the game camera has to tilt upwards to view a Colossus, magnifying the appearance of its height. Another trick they used to magnify the already considerable size of the Colossi is by filling the game world with terrain that dwarfs the hero, and then making the Colossi even bigger than that terrain. I am pretty sure they are slightly upping the size of the Colossi as the game proceeds too in order to keep the "wow!" factor going.
The one area where the developer's careful eye to detail really shines is in the physics and movement of Wander and the Colossi. The hero's movements are not stiff or simple. Rather, he is always stumbling as he gets up after a jump, walking unsteadily across a moving surface, and being thrown around like a rag doll as he desperately holds onto a gigantic monster's shaking back for dear life. The way the Colossi walk around, shake their heads and backs, and flinch from bow or sword hits is also very natural looking and life-like; the Colossi convincingly behave like living creatures. Furthermore, the way they visibly tear the ground apart with each step and create massive screen-blurring shockwaves with their attacks strongly emphasizes the incredible power that their size gives them. The physics of the game is important to this overall effect too, since the hero really can be pitched from the back of a Colossus if the player makes a single misstep.
Most of all, the experience of fighting a Colossus is so strong and exciting because it is an honest, fun challenge. Fighting a Colossus has all of the elements of a boss-fight, a platformer stage, and a puzzle rolled into one fluid package. Since the Colossi are always moving, reacting, and attacking, the player has to constantly stay alert and keep his eyes on what it is doing. At the same time, getting into position to attack a Colossus's weakpoint is never a simple process since it involves exploiting the terrain, tricking the Colossus into doing something stupid, and/or hampering the Colossus with well-placed attacks. The game also has incredible platformer elements: while I have made a lot of jumps in a lot of videogames, I have never made a death-defying jump from a monster's swinging elbow to its waist before. Shadow of the Colossus expertly melds all of these game elements into a single fast-paced, visually stunning thrill ride.