I was thinking about this plot right now, and I thought it was very dark and pretty cool:

In the beginning, there's this common Final Fantasy-ish style to it all, pretty much like FF9.
However, one day a dark power makes different kingdoms and cities making war upon each other, and evil rises between all sorts of people.
The evil aspects start off slowly, but go more and more perilous.
This dark power is very unknown at first, and all that we know is that SOMETHING out there makes people go mad.
Its goal is to make everybody destroy each other, and so on.

I think this plot has got some potential, but I'm not fully sure.