It pretty much seems like they've generalized most legendaries as Dragon type Pokemon, and it's not really something I like. I guess this kinda comes off the designers often basing legendary Pokemon on mythological creatures, whereas a lot of those are or relate to dragons, in which case a lot of them end up being Dragon types, however I'd just really like to see some more creativity and variation. Give us some more Bug, Dark, Fighting, etc. legendaries, instead of throwing the same typed legendaries at us all the time. It'd also open up for a lot of different themed legendaries, although I guess that's also harder than the typical dragons.
I agree with Olli there. Sure dragons have there place in myths, but so do many other creatures. They've done dragon-based legendaries for about 3 Gens now, so it's about time they try something else. And there are other strong types in the Pokemon world apart from Dragon, like Dark and Psychic.
A Bug-type legendary would be interesting to see, don't you agree? Something like Volcarona, but stronger!