Going from a wireframe model to a shaded model requires some kind of texturing. In real-time 3D games, such as Shadow of the Colossus the textures must be small enough so that you can move about the scene without requiring too much computing power. As computers and game consoles become more powerful the textures can be made larger and more detailed. New methods are being tested which will allow game engines to use textures in a new way to give you more detail and less repetition for less computing power. There is an interesting article discussing this at Game Within.