Never a big fan of DD either really except for some of the later issues, but it was his early work. Anyways, its not really the "drawing" per se that sets Miller apart. He's not trying to outdraw frazetta. He's trying to use each frame to tell a story in the way a movie would. 8 panels of Kingpin smoking a cigar in the pitch black because that sets the mood as the shadowly underworld villain he's supposed to be. Now maybe that's not your cup of tea but the point is, he's not trying to draw the most beautiful art he can. He's trying to illustrate the most impactful story he can. Those are very different things and he was extremely successful at creating impact, so much so that the impact went past the printed page and even changed the course of the industry.
Similar idea for Barks in that its not his drawing that sets him apart, its the writing, its the life the characters are infused with. Same for Crumb - he can draw but its not the drawing. Its the look into human nature with him.
In a way, its not fair to compare artists that are also writers to artists that purely illustrate but you can't really stop it from happening because writing often gets marginalized and a good --script can be ruined pretty quickly by bad art.
Gibbons isn't special at all, but he illustrated Alan Moore. If he had illustrated the writings of Joe Shmucklack neither one of us would even know his name.