I saw this movie only once in a cinema, as a child, shortly after it was released. I still remembered scenes and bits of it more than 20 years later! I recall feeling particularly moved by the poor people kept captive underground, which evidences that children's stories must not necessarily be devoid of suffering and injustice. On the contrary: this kind of plot may feed children's sense of indignation and thus ultimately contribute to a better world.
This film is one of those rare pieces of art that are a true explosion of fantasy that will capture a child's imagination completely, combined with an underlying message that will also fascinate adults.
I bought the superbly produced "Édition Collector 2 DVD" set (Zone 2) through Amazon France about a year ago and it has become one of the favorite movies of my 5-year-old son, too, although neither of us speaks a word of French...