Yeah and because they used pre-rendered backgrounds, the scenes couldn't move.
Games can use pre-rendered textures also that already have shadows, etc implanted within them.
Nowadays though, most of the effects can all be done in real time within games, and if some effects aren't, theres alot of limits placed upon the engine which is never good.
Soon I suspect pre-rendered movies like the newly released Ice Age 2 (excellent film) will be able to be animated and rendered out in real time, taking just the films length to finish.
The reason they take so long to render is simply because the video card is hardly used. Mostly all the work is being placed on the CPU, for ray-tracing, etc which is why the task is so tedious, being that most CPU's can only do one thing at once, and a latest graphics card can do 48!