Yes, Stan Lee is technically one of the main architects of the Marvel universe. That's why he gets all of those cameos. Whilst he should probably split most of his acclaim equally with his artists in most cases since Jack Kirby, Steve Ditko etc had as much to do with developing the characters of Spider-Man, the Avengers etc he can claim essentially no credit for the X-Men of today. The original X-Men were on the verge of cancellation when Lee was in charge. The book sold so little copies a month it went into reprints pretty quickly, and it was Chris Claremont (mostly with Dave Cockrum and John Byrne) who made them the big stars of today. Which was helped by the movies, which mainly drew on Claremont stories. Claremont made the X-Men slightly more realistic, believable, grounded if not in the real world then realistic sci-fi. Lee, meanwhile, had everybody macking on Jean Grey, Iceman look like a snow man, Magneto wielding powers that had nothing to do with magnetism (he could hypnotise people thanks to his magnetic personality), and tonnes of other goofy stuff. All comics from the sixties have their silly moments. But man, Stan Lee's X-Men just seemed to have even more than usual. Plus Magneto seemed to have a weird thing for his daughter...