I agree that just because a movie is good doesn't mean it warrants an attraction. The Hunchback of Notre Dame is one of my favorite Disney films, but with it's somber tone and subject matter I don't think it's very suited for a "ride" at Disney World. Frollo, despite being a great character, sorta feels out of place when he shows up with the Disney villains in Fantasmic and other events.
Same goes for movies like Bambi and the Fox and the Hound. Good stuff, but I can't think of a ride that would suit them. Many are indifferent to James Cameron's Avatar as a movie, but agree that the land in Animal Kingdom is really cool and that Flight of Passage is a great ride.
I do think that if Splash Mountain had to be rethemed, the Princess and the Frog is an extremely good fit due to its bayou setting. The fireflies and Dr. Facillier's Friends on the Other Side could also lend themselves well to impressive lighting effects.