Well you guys got to talk about Digimon, so I'm going to drone on about Stargate and the fact that no-one can agree on a definition of God.
The original Stargate villians were a race known as the Goa'uld, a race of parasites that had access to some very advanced technology including a device that allowed them to live for millenia and resurect the dead. (The corpse has to be fresh.) They convinced less technologically advanced races that they were gods and insisted they be worshiped as such. After thousands of years of this many of them statrted buying their own PR and actually started believing they were gods figuring worship=godhood. Despite all this they were definitly killable and any sufficently tchnologically advanced race could tell they were using smoke and mirrors, though the Goa'uld's followers honestly believed they were both onimotent and immortal.
Later came the Ori, a group of "Ascended" beings with insane powers. Being ascended basically means they are energy beings that live on a "higher plane of existence" are omnipotent and basically have limitless power. However they are bared from acting because of another group of ascended beings that absolutly insist on non-inteference with the mortal plane. The point is that despite all their incredible powers most poeple refuse to actually refer to them as gods, largely because of the past problems with the Goa'uld. These people usually point out that the Ori used to be mortal beings long ago, before ascending, and that despite all their powers they did not create the universe nor have they existed before the begining of time. They even point out that the existence of the Ori does not prove there isn't a God that is more powerful than them.
So basically, the qualifications for being a god really depend on who you ask. As for Celestia and Luna? As far as we know they are immortal, and they have the power to rasie and lower celestial bodies. That's nothing to sneeze at.
edited 8th Dec '11 6:27:24 PM by WillKeaton