Before they settled down a more permanent home in the Avengers, Hank Pym's Ant-Man and Janet van Dyne's the Wasp had adventures in Tales to Astonish from 1962 to 1965. Stan Lee, Jack Kirby, Larry Lieber, Don Heck and Dick Ayers gave the two tiny heroes a relatively small rogues' gallery of villains including the Living Eraser, Egghead and Porcupine. By the time Ant-Man grew out of the title, Lee had co-created approximately 35 characters.
While the Hulk might be the strongest one there is, his series wasn't a smash success when it started in 1962. However, Stan Lee and Jack Kirby brought the Green Goliath to Tales to Astonish after Hulk's first series ended. Besides Kirby, Lee worked with artists including Steve Ditko, John Romita, Herb Trimpe and Marie Severin on the series and the first few issues of Hulk's second solo series.
By the time he stopped writing the character in 1969, Lee had co-created approximately 50 characters, ranging from the Hulk to villains like the second Ringmaster, Abomination and Boomerang.
After debuting in 1962's Amazing Fantasy #15, Stan Lee and Steve Ditko's Spider-Man wall-crawled his way into becoming Marvel's signature hero. Lee and Ditko worked together on Spider-Man's subsequent series, The Amazing Spider-Man, for 38 issues and a few annuals, where they created Marvel's deepest supporting cast and best roster of villains.
While John Romita, Don Heck, Jim Mooney and Gil Kane took over on art, Lee stayed on as Spider-Man's regular writer until 1971's Amazing Spider-Man #100. By the time he left the series for good in 1973, after writing another 18 issues, Lee had co-created roughly 120 characters.
While Stan Lee and Jack Kirby created plenty of characters together, Thor gave them the chance to build the world of Asgard in Journey Into Mystery and Thor. With some early scripting assist from Larry Lieber, Lee and Kirby worked together on Thor from 1962 to 1970, with Thor's modern adventures occasionally supplemented by the "Tales of Asgard" back-up feature.
After Kirby left, Lee continued working on comics with John Buscema through 1971. By the time Lee left, he had co-created approximately 190 Thor characters.
Stan Lee, Don Heck, Larry Lieber and Jack Kirby all worked together to create Iron Man in 1963's Tales of Suspense #39. As Tony Stark's earliest adventures carried on, Robert Bernstein, Steve Ditko and Gene Colan also worked on the series. Lee stopped writing Iron Man just before the hero's solo series launched in 1968. During his time on the title, Lee co-created roughly 50 characters, including future Avengers, Black Widow and Hawkeye.
In 1963's aptly-named Strange Tales #110, Stan Lee and Steve Ditko created Doctor Strange, the Master of the Mystic Arts. After working on the series for three years, Ditko left in 1966. After some quick runs with Bill Everett and Marie Severin, Lee followed suite in 1967, having created roughly 50 characters on the more magical, cosmic and psychedelic corners of the Marvel Universe.
Starting in 1963, Stan Lee, Jack Kirby, and later, Dick Ayers, chronicled the WWII-era adventures of Nick Fury in Sgt. Fury and His Howling Commandos. While that series was still going on, Lee and Kirby started looking at Fury's subsequent tenure as S.H.I.E.L.D.'s most famous agent in 1965's Strange Tales #135. Between his work on those two comics, Lee co-created approximately 45 characters, mainly soldiers and spies, in his Fury tales.
Even though Stan Lee and Jack Kirby created the X-Men in 1963, the mutants didn't fully come into their own for another decade or so. With some assists from Werner Roth, Kirby worked on The X-Men for 17 issues. Just two issues after that, Lee concluded his relatively short run on the series, having co-created roughly 45 of Marvel's merry mutants and their compatriots, including other heroes like the second Ka-Zar, Scarlet Witch and Quicksilver.
With The Avengers, Stan Lee and Jack Kirby brought some of the biggest names in the Marvel Universe together in 1963. After 17 issues of The Avengers, Kirby left, and Don Heck took over for the rest of Lee's run. Although Lee worked on the series for 35 total issues, he only co-created about 40 characters for the series, since it featured so many pre-existing heroes and villains.
Before he was the dark, brooding character he is today, Daredevil was the Man Without Fear when he was created by Stan Lee and Bill Everett in 1964. Over five years and 50 issues on the title, Lee co-created about 45 characters with Jack Kirby, Wally Wood, John Romita and Gene Colan.
Stan Lee and Jack Kirby revived Namor in Fantastic Four, and the Sub-Mariner starred in 31 issues of Tales to Astonish. Lee wrote 22 of those issues and co-created roughly 10 new characters with Kirby, Gene Colan and Marie Severin.
Similarly, Stan Lee and Jack Kirby revived Captain America in Avengers. The Sentinel of Liberty got his own feature in 1964's Tales of Suspense #58 before graduating to his own series in 1968. Kirby worked with Lee on Cap's adventures until 1969. Lee continued writing Captain America and working with Jim Steranko, John Romita and Gene Colan until 1971. During that run, Lee co-created about 60 more characters.
With Gene Colan, Lee wrote the debut of Marvel's first Captain Marvel, where he co-created another five cosmic characters. Even though the Silver Surfer's first series only lasted for 18 issues, Stan Lee wrote all of them. Working with John Buscema, Jack Kirby and Moebius, he created about 15 characters for the series and its follow-up graphic novels.
In 1977, Stan Lee and John Romita started working on The Amazing Spider-Man newspaper comic strip. Fred Kida and later Larry Lieber took over art chores, and Lieber only retired from the strip in September. Lee and his collaborators kept this corner of the Marvel Universe going and introduced around 50 unique characters in this strip.
After he stepped down as Editor-in-Chief in 1972, Stan Lee's comic book work got a lot more sporadic as he became more of an ambassador. While he returned to write the first appearance of She-Hulk in 1980 and a few other specials, Lee didn't take on another regular writing gig until 1992's Ravage 2099, which he worked on with Paul Ryan for seven issues. Altogether, Lee created about 15 characters in this period. For the last few decades, Stan Lee only really returned to Marvel to write short stories in special anniversary issues.
Along with his collaborators, Stan Lee had a hand in the creation of approximately 1,225 Marvel characters, by our estimation. While a number like that might be quantifiable, it's impossible to quantify the influence that Lee had over Marvel, the superhero genre and comics as a whole. Between his immense, impossibly deep body of work and tireless personality, Stan Lee and the body of work he produced were, quite simply, marvels.