Uhm...
Pre-Rendered means the backdrop, or certain assets of the scene are already rendered to a set location, and cannot move, change, or have any changing properties (for the most part).
PSX games used this VERY heavily since it was easy to use the vast amounts of space that PSX CDs had, to make the graphically inferior CPU/GPU "look" better compared to other games on the N64, and somewhat on the Saturn. FFVII and RE 1-3 were great titles that used it.
A game fully produced in 3d has no such properties - each object can be seen, and viewed from each and every side, and has to be rendered on the fly depending on where the camera is.
Easiest way to explain it is that your comparing a painting, to a person. One is flat, the other isn't.
Back from the dead, I'm afraid.
