"Over the years, when he heard somebody liked other artists more than his work, he was really non-competitive. The thing, though, that I think a lot of people never got about Jack was that Jack wasn't really competitive with most other comic book artists, because in his mind, they had a different job description. When John Buscema sat down to draw an issue of Fantastic Four -- and, actually, nothing I'm about to say is knocking John Buscema in any way, or any of the artists I'm going to mention here -- his goal was to do an issue of the Fantastic Four. When Jack sat down to do an issue of Fantastic Four, in his mind his job description was to create a new universe, three spinoffs and take comics to another level."
Note: The original version of this post misattributed the comment. It's been edited to correct that, and to provide a fuller quote.