He's Greenwood, or the avatar of Greenwood.
Ed has said himself that Elminster was a character created when he was a child so it is not likely that he is Ed's avatar even though Ed has physically grown into Elminster in real life.
He's Greenwood, or the avatar of Greenwood.
I kinda figured he was like Hercules or Achilles - everyone knows about Troy and the 12 Tasks of Hercules, even if they don't know the detail of the story. What adventures do people know about where Elminster is the central figure? Or is he the fantasy equivalent of Kim Kardashian?
Oh and as far as the Marie Sue thing, he did seem to have an awful lot of success with the ladies.