Spider-Man is Marvel's #1 Super-Hero. There is no doubt about that, despite the popularity of the Hulk, Wolverine and other heroes featured in today's films. But when did it actually happen?
Marvel had been promoting Fantastic Four as "The World's Greatest Comic Magazine" and there was little debate that it was. But Amazing Spider-Man overtook it as the company's flagship title, probably in 1966 when Steve Ditko left and John Romita began drawing it. There were, of course, stylistic and thematic changes from the start. The supporting cast and Spider-Man/Peter Parker got less acerbic and more dramatic. The tone was less downbeat and more romantic. Peter wasn't 100% a whining loser anymore and there were positive influences in his life in Gwen Stacy and Joe Robertson.
1966 also saw The Marvel Super-Heroes cartoon series debut. Though one would be hard-pressed to call them "animated", viewers were able to enjoy the adventures of Captain America, the Hulk, Thor, Iron Man and the Sub-Mariner and their catchy opening themes.
This led to 1967's Fantastic Four and Spider-Man Saturday Morning cartoons. Both had good points and bad points but Spider-man was more memorable, edgier and lasted longer. And it had one of TV's most enduring theme songs! While the classic Ditko villains were all there, John Romita's recent additions were also included in the Rhino, Kingpin and the second Vulture (the design at least). This would seem to correspond with John Romita's stock rising in Marvel after the departure of Steve Ditko and would even be greater than Jack Kirby's, all due to the growing stature of Spider-Man.
This was more apparent in 1968 with the black & white magazine/experiment, Spectacular Spider-Man. This was an attempt to expand Marvel's presence on the "mainstream" magazine racks. It's telling that they went with the Wall-Crawler instead of the FF or Captain America. Despite its failure, it also showed Marvel's faith in the character.
By that point, Spider-Man was Marvel's icon in the days of multiple Superman titles and Bat-Mania.
So at what point did Spider-Man assume the mantle of #1? And what convinced you that he was?