If we're talking about the main FF games (and not XI either), I would have to go with XII.
XII had some serious flaws, but with a few fixes it could be really good.
Gambit System -- If they had just given us access to all or most of the gambits from the get go, it would be quite good. By the time I actually started getting interesting gambits, I stopped caring about the system.
License Grid -- It would be good if every character didn't have the same grid. Since it has the same grid, every character ends up being exactly the same.








