Shadow of the Colossus was a special game, with many wonderful features, too numerous to go into here. If there is one thing that SotC does right, and arguably better than any other game, it's animation.
Animations are the glue that bind video games into cohesive wholes: we notice it when it isn't there or incongruous, but when it is it disappears. Animation is always used to communicate something, be it the weight of a character - in its ponderous, lumbering movements - or the safety of a rickety bridge, swaying ominously in the wind. It's also used as a method of transition, moving objects in the game world from one place to another.
SotC, however, brings animation to the forefront, by fully utilising it as a communication of emotion, not just a method of transition.
What do I mean by this? Let's take a normal transitive animation: walking from left to right. A character moves from one position to another. Perhaps he is running, perhaps not. The walking animation creates a congruous meaning to the movement, so that the character is not "skating" to a new position. However, when the lead character moves in Shadow of the Colossus, he scrambles, almost toppling head over heels. When climbing a colossus, it's a desperate venture full of cart-wheeling falls and near-death grasps. Your finger clenches tighter on R1, becoming the medium by which you will the character to cling tighter, watching in raptured suspense as he is tossed and turned by the angry beast. You're not just moving from one place on the colossus to another. The animation is communicating the peril.
One can only hope that with procedural animation engines like Euphoria taking over the menial tasks of animation, that skilled, talented animators will be able to spend greater time on looking at expressing the visceral, the joy or the pain of the characters on-screen, directly and without words.
It's a wonderful achievement that Wander says so little throughout the game, but communicates to you everything.