I wouldn't say superb as it was missing a few bits, and at times seemed a bit rushed..
Action scenes in the movie were superb and were meant to be unrealistic as it is a fantasy movie meaning anything is possible. It can get quite confusing at times, but overall the plot is better then most basic and boring storylines I have come to see in RPG's such as the "save the pricess" or "kill the godly monster" (FF10) .
It would however have been great to witness Jenova's power on screen, but unfortunatly we were only given a glimpse of her, we did see Sephiroth, but he didn't give us enough action and he was defeated before you could even get excited about his return.
It was have been excellent to feature some of the Summons such as well known Ifrit, Shiva and Brahamut, I am sure they would have really made the movie all that much more interesting.
The other characters didn't get enough attention although you did see them fight a bit, but they were meant to be a team and if Cloud was so powerful as they made him out to be, they might as well not feature the others at all.
Besides all of the flaws, the movie was excellent, hopefully we'll see some Ifrit, Shiva and Brahamut action in another movie.