Don't you feel that this opinion is a totally western bias. And really just a US/England bias? When it's stated that he's the best ever, EVER. In all of comics the more I think of it the more I find faults. I love Watchmen, I have the Absolute-first printing, I can't say I like it more than Akira and Calvin and Hobbes. I can't say I love LoEG more than Snoopy finding his family in Peanuts. I can't to me that V for Vendetta is better than Doonsberry in the 80s. To me the For the Man Who Has Everything is great but so is that Mobeius Silver Surfer book. I think to call him the best I really think it should be agreed upon by a wider audience than just American comic book readers. Maybe the term that should be used is best American Comic book writer ever, cause that might be what he really is, and not the G.O.A.T.
It is not a bias with me. I have a huge bias against all things British (it is entirely illogical, I know, but it stems from being brought up in a heavily Irish household), and yet I think Alan Moore is the greatest writer of comics that I have read. I have read Akira and Calvin and Hobbes, Peanuts and Doonsberry, and a ton of Moebius' airtight garage universe; but I still think that Moore is the greatest consistent writer. Are their individual works better than any of his individual works? Absolutely! Does that mean that the writer of that work is a better writer than Moore? no. Is Roger Maris a better ballplayer than Babe Ruth because he had more homeruns in a single year?
I will freely admit that I haven't read much "Eastern" comic work (outside of Pluto, 3 volumes of Akira, and some Blood+), so I may revise my personal opinion of Moore as the greatest writer in the history of comics, but that is why they are opinions. I surely cannot speak for anyone else here, so my opinion of Moore is quite probably different than everyone elses.
Moore's status in each individual's eyes is besides the point, though. Other users have been absolutely correct that this shouldn't become a Moore Vs. Aaron debate. We should not let our enjoyment of the works be clouded by this little event (which I'm sure will be entirely forgotten before long).