Of course, I wouldn't put it past Fraction to have copied the concept from Gaiman, Moore or any number of authors. The problem is that Fraction is no Gaiman or Morrison; he doesn't quite possess the skill to fit high concept into conventional Superhero storytelling. Jason Aaron, on the other hand, is quite talented (even though I was rather confused by his Hulk run, I am a huge fan of Scalped). His examination of "what it means to be a God" insofar as what he's doing in Thor God of Thunder seems like a more deft approach to the role of Gods in a superhero universe, particularly given the confines of the Superhero genre (i.e. the heavy role of continuity) and its tropes and conventions. That is to say, it's easier to portray a "God" as being a benevolent super-powered being who exists across vast swaths of time than it is to disregard established continuity in service of the idea that "myths are unreliable" as Fraction attempted (and failed) to do during his Thor run.
On another tangent -- and to touch on the Brief Lives story briefly, some old gods, like Bast have been greatly diminished as they've been forgotten while others, like Pharamond have found a way to adapt. In a very superficial way, Pharamond's adaptation to the evolution of belief is similar to the way that Thor and the Asgardians have adapted to their changing role over the millenia. However, unlike Pharamond, Thor was never "powered" by his followers' belief to begin with. Thor's puissance is a function of physical characteristics independent of whether he has followers or not, hence the evolution of the Marvel's Norse pantheon from deific beings (as was intended by Kirby/Lee) to a quasi-alien race (as is the current treatment in line with the movie property). Interestingly, because the Norse pantheon is a central fixture of the Marvel mythos (a function of Thor's own centrality to the overall Marvel myth narrative) this distinction has been applied primarily to them but it should be applied across all the mythological pantheons of the Marvel Universe since the different pantheons mutually acknowledge the others as fellow "Gods/Immortals."