I don't really like how Mewtwo has become so overshadowed by the likes of Arceus and now these dragons. He was originally intended to be the most powerful Pokemon in existence.
I know you can argue that Arceus is "the creator of all Pokemon," but I really hate that role. Nintendo shouldn't have gone there.
And I can understand that these guys are two legends fused together, but I still wish they had just gone with one, "Perfect Fusion." I think I would have been ok if that had surpassed even Mewtwo.