I have never been satisfied with the idea that Godzilla was nothing more that a radioactive (and somehow resurrected) dinosaur. In the 2014 version of the film the writers suggest what seems to me to be a much more satisfying origin for Godzilla and perhaps all other Kaiju. The film goes over this very quickly and without much detail, but the suggestion is that Godzilla predates the dinosaurs by perhaps millions of years, that feeds off of radioactivity, and does not "eat" in any sense of the word that we would recognize. The filmmakers go on to suggest that as the primordial earth started to cool, and presumably became less radioactive, Godzilla and the other Kaiju went into a dormant state close to the planet's core. I like this explanation because it gives the Kaiju a much more mythic and grand origin. It also fits in well with Lovecraft's idea of the elder gods. Perhaps the Kaiju are even older than the earth. Perhaps they represent a form of creature that developed shortly after the big bang and traveled through space in a state of hibernation; waking only in the presence of radioactivity. In this scenario Godzilla is of extraterrestrial origin and much older that has ever been suggested before.