I was pleasantly taken aback by this film. It becomes this balancing act between being dramatic and serious to being fantastical, silly, and even funny. It demonstrates the harshness of adult responsibilities, but also the innocent imagination that exists in the young. Both Robin Williams and Dustin Hoffman delightfully play the hero and villain respectfully with hammy joy.
Some will take issue with the third act's plotholes and that is understandable, but I'd argue that they serve to strengthen the fairy tale aspects of the film because in the end, it IS a fairy tale where both perfection and reality are disposed of.