Well, both are very Tolkien-esque fantasy universes. And Dragons are pretty standard fare in this type of fantasy. There are also elves and such, so I don't think they are really ripping each other off or anything.
If anything, they both rip of LOTR, but that is pretty much standard as Tolkien defined fantasy.
This seems to be a very important thing, moreso than most. In the end, I think this very detail created the MW/Oblivion schism. Morrowind was NOT a tolkien-esque land, and it was really original in scope. Then when Cyrodiil came to the forefront, it, well, looked like most of the world would. Morrowind was the exception, and i think that confused a lot of people. But at least Bethesda knows what to use and what to discard..(I dont think ive ever heard any mention to maximum age of human or elf in ES.) Some games just either pretend they arent following the legacy. Others, well, they embrace it fully. in the Rifts pen and paper RPG, theres a city of magic named Tolkien. Yes, its named after him, the inhabitants readily admitting so.