Yes, there were dragons. Not to put a damper on Humans or anything though we are creative and intelligent we are not that creative to make up this elaborate monster to talk about in different cultures of the world. I do not believe in all the dinosaurs became extinct from the meteor shower. If they did why are their reptiles, birds, Komodo Dragons, or other direct descendents of the dinosaurs. I feel that the dragon was nothing like a T REX but another large dinosaur(perhaps one of the herbivores) that people saw and needed to destroy. Or in the Chinese's case harness its powers.
There is a theory that some scholars believe that some of the myths of Ancient Greece were from the Greeks finding fossils of prehistoric creatures. For instance the Cyclops= Wooly Mammoth. All that could be seen was the "hole" for its trunk which looked like it only had one eye. Possibly creatures of the dragon legend was looking at fossils of dinosaurs and in trying to explain it to the best of their ability they claimed it to be a dragon.