Odin and Ragnarok are Norse, not Greek. You're thinking of Zeus and Prometheus. (I don't think Prometheus is the end of the world, but it was some kind of disaster, as well as being the giant who gave fire to the humans).
In the French version of Final Fantasy 8, Quezalcoatl is called "Golgotha", the hill upon which Jesus was crucified, though "Golgoth" on its own in French means "Gigas". Also, one of my friends when playing the game inexplicably renamed "Quezacotl" to "Garuda". When I asked why he'd done that, he said that he didn't know, it just felt right. It kind of does actually; Garuda's one of the FF11 servers and they're all named after summons.
Still on the subject of French FF8, the Ragnarok is the "Hydre" (Hydra, a multi-headed dragon-serpent thing that the Greek hero Hercules defeated).
Shiva and Ifrit keep their original names, oddly enough. They're among the very few that do. However, Shiva's "Diamond Dust" is now called "Transcendentale" (Transcontinental) and "Hellfire" becomes "Divine Comédie", after Danté's Divine Comedy... ^____^
Siren is "Ondine"; "Onde" means a radio wave in French, so there's no mythical connection this time.
Sacred and Minotaur are known as "Tauros" and "Taurux" (forgot the order) and are collectively known as "Taurus", pretty straightforward.
Carbuncle is "Ahuri". That's the French word for the less glamorous meaning of "Carbuncle"; a zit or something similar on flesh, as opposed to a semi-precious stone similar to a ruby but darker.
Leviathan keeps its original name, as does Cerberus, but with the French spelling which I can't remember right now.
Pandemonia is "Zéphyr", a type of really strong wind or something.
Alexander is unchanged.
Doomtrain is "Helltrain". Ah well. At least his attack has a cool new name, "Death Express".
Bahamut's name is the same, but "Mega Flare" is now called "Ourobouros"! I think that's a dragon swallowing its own tail, a mythological representation of infinity.
Tonberry is "Tomberry", which is just an alternate interpretation of the Japanese spelling.
Cactuar is "Pampa". I have no idea what this means, and my French is no longer well-practiced enough for me to understand the fr.wikipedia.org's entry on it.
Eden is "Orbital". Right.
Griever becomes "Cronos", a Greek god that symbolises time. A bit (or rather, a lot) of a departure from "something that grieves" but given the whole Time Compression thing it kind of works.
Not mythical or anything, but Laguna's "Machine Gun" is named in the status menu as "Kalachnikov". Also, Quistis has a whip called "Totally S.M.", with that actual English name.
More as I remember them, or replay the French version; I'm thinking of doing a continuously updated thread in the FF8 forum about it, taking screenshots as I go because the translation differs so much.