I never finished FFVII. Only played 20 hours of it before getting really tired of it. I like the story and the characters but hate the materia/leveling system. After playing FFX I don't think I can ever go back. Although the story and characters aren't as good, it has better balance, battle system, leveling system, better pace, and the graphics are leaps and bounds ahead of its predecessor.
If I go back to playing older FF, I would play the 2D games: FFI-FFVI. I still think FFVI is Squaresoft's crowning achievement. If Square should ever go back and do a remake that should be the one.