It was a very good movie, however they could've done so much more. Such as a make a FF Sequel that didn't suck for one. And they could've made mention to the Gold Saucer and many other in game things such as the Weapons. But the whole reason to my understanding why they never made a sequel and why the movie didn't come out for a while is because the game didn't have a happy ending, it made you think humanity was blinked out existence when Holy happened. The most notable hints being RED XIII's little run and the sight of Midgar at the end.
But also one conversation in Cosmo Canyon:
Bugenhagen: The knowledge of the Ancients swirling
around here is telling me one thing. The planet's in a
crisis...A crisis beyond human power or endless time. It
says when the time comes, we must search for 'Holy.'
Cloud: Holy?
Bugenhagen: Holy...the ultimate White Magic. Magic
that might stand against Meteor. Perhaps our last hope to
save the planet from Meteor. If a soul seeking Holy reaches
the Planet, it will appear. Ho, Ho, Hoooo. Meteor, Weapon,
everything will disappear. PERHAPS, even ourselves.
Cloud: Even us?
Bugenhagen: It is up to the planet to decide. What
is best for the Planet. What is bad for the Planet. All that is bad will disappear. That is all. Hoo, hoo, hoo, I wonder
which we humans are?
But there are many clues in game that say humanity isn't gone. Such as the sound of children laughing at the very end, Holy saving the Highwind, and Holy purifying Cloud. It would have been nice if the movie touched on the subject. But oh well it's still pretty f***ing good.
And for some more FFVII mythology to think about go here:
The true meaning of Final Fantasy VII