Kyuubi and Ninetales are both based on the same myth, not ripped from each other.
Exactly, it´s based on a mythical japanese creature the kitsune.
I´ve seen 4 or 5 animes/games with this kind of creature.
Besides Pokémon and Naruto, I´ve seen this creature in
Digimon:
With Kyuubimon.
Ragnarok:
There´s a monster in Ragnarok called nine-tail.
And another one that I don´t remember right now...:P
Besides that, there are other pokémon based on other mythical creatures, like Ho-oh and Arcanine.
Ho-oh is based on the Phoenix (wich is used in a lot of games and animes, like Final Fantasy, Digimon, Pokémon, Harry Potter, Monster Rancher, Medabots, etc, to list some XD)
And Arcanine is based in a mythical chinese creature: Shisa, a cross between a dog and a lion:
And although its a canine pokémon, Arcanine is also based on a real life feline: the Liger (a cross between a lion and a tiger):
Arcanine comes from the words canine and arcanos (I named my Arcanine like that ;))
I hate when I give this kind of explanation, but here you go, and I hope you find it interesting. ^^"