Today I am very sure that the cut scenes in god of war 3 are pre-rendered not real-time rendering.
The way I figured out is that the shadow looks very very nicer and softer on the pre-rendered cut scenes while the shadow isn't that much smooth during the game play.
I should say it was almost indistinguishable if I didn't pay enough attention on the shadow.
It is often hard tasks to match the pre-rendered cut scenes and the actual game scenes, because 3DS Max or Maya generates quite different look and feel of the background or characters from what the actual game engine generates. I am guessing that they might have pre-rendering tools with the game engine, not directly from Max/Maya.
It could probably save some face motion animation data by using pre-rendered cut scenes.