The first movie (Final Fantasy: The Spirits Within) followed the premise of all the Final Fantasies, being that its story was completely and totally unrelated to the others. That aside, I enjoyed it. And so did my girlfriend, and the friends I took to see it. So I dunno.
More to the point though, recently Square has been breaking its rule where all Final Fantasies are different worlds, with Final Fantasy X-2 coming out sometime soon. The new movie (Final Fantasy: Advent Children) is the 'secret' Final Fantasy VII-2 project I've been hearing so much about.
(Final Fantasy VII was one of the most popular Final Fantasies in the states, and in large part helped catapault the series into the popularity it currently holds today)