There is no difference in quality between the PSX and PC movies. None. Besides that, many of the movies would have to be chopped and re-edited. The fact of the matter is that what may be one movie on the PC is often on PSX the first half of one video file and the second half of another. Or two movies might be squeezed into one video. To top that off, the music files on PC are part of the movie, but on PSX they are played from Midi. So reincoded PSX movies will have sound effects, but no music.
Reincoding the PSX version movies will be a long and strenuous process with no quality improvement of any worth.
However, one alternative might be to reincode the PSX version movies limited to 16 bit color. The reincoding process would probably render better results then FF7's antique on-the-fly playback, and the movie wouldn't lose any color depth in the process.
Just a thought.
-Contra-