I would like to toss The Flight of Dragons into the fray.
As a dragon movie, I could say it was fairly decent, except by some flaws (the main flaw in my opinion would be the "main" character which would be the equivalent of that one guy whom you kick out of D&D sessions because he overthinks stuff and stalls the entire campaign). That, and because the climatic final battle was rather, well, anticlimatic... (A perfect example of Talking the Monster to Death)
Otherwise it was a rather enjoyable movie.
Also, it was one movie that pretty much explained the dragons' capability of flight as them simply being like blimps.
There's also "Dragons, a Fantasy made Real"; a "documentary" by Animal Planet that pondered the possibilities of their existance.
Oh that's right I almost forgot about Flight of Dragons movie that was a very well done movie back when Animated movies were beginning to become a respected entertainment medium.
Yea I saw that dragons documentary oh boy do I wish that was real I would be so excited I would make sure I was one of the first people to see the exhibit.
