There can be no doubt that Stan Lee revolutionised the comic book industry in the Sixties. Prior to the creation of The Fantastic Four, most superheroes were idealised and nearly perfect. On the other hand, Lee made his heroes flawed, with realistic personality traits. The Fantastic Four bickered among themselves. Spider-Man was basically a nerd who was plagued with self-doubt even when in costume. The X-Men were mutants who were hated by the rest of society. Lee showed unusual originality in giving his characters actual personalities and challenging storylines.
But in some respects the characters Stan Lee created were not particularly original. Often their super powers had been used before for comic book heroes. In some cases they seemed very similar to previous superheroes. While Lee was very original in his treatment of superheroes, he was sometimes not particularly original in the powers he endowed them.
Examples of this can be found in The Fantastic Four. As most comic book fans know, Johnny Storm was not the first Human Torch. The original Human Torch was created by Carl Burgos and appeared in the first Marvel comic book ever published, Marvel Comics #1, October 1939. Unlike Johnny, the original Human Torch was not a human who gained his powers through an accident, but an android created by Dr. Phineas T. Horton. The original Torch appeared in his own magazine until March 1949. He would eventually appear in the Silver Age, meeting his namesake in Fantastic Four Annual #4, 1966.
Of course, creating new versions of old characters was nothing new at the time. In fact, the Silver Age had begun when DC created a new version of The Flash in 1956. They would follow up that success with new versions of Green Lantern, The Atom, and Hawkman. But Johnny Storm was not the only Fantastic Four member whose powers were nothing original. Reed Richards, Mr. Fantastic, has the ability to stretch into any shape he wants, precisely the same power that Quality Comics' Plastic Man possessed. Plastic Man was created by Jack Cole and first appeared in Police Comics #1, August 1941. He was probably Quality's most popular character besides Blackhawk and was one of the few Golden Age heroes to actually survive the Golden Age. Reed Richards was even pre-dated by DC Comics' own stretchable hero, the Elongated Man, who first appeared in The Flash, vol. 1 #112, April 1960. Even then, the only reason Julius Schwartz created the Elongated Man is that he didn't know DC had acquired Plastic Man among their takeover of Quality characters. It must be pointed out that even Mr. Fantastic's genius and invention of gadgets has precedents. Doc Savage, like Reed Richards, was a multi-talented genius.
While members of The Fantastic Four duplicated powers of previous superheroes, Spider-Man not only duplicated the powers of a previous hero to a degree, but even the background of the hero. In fact, there has even been some controversy over the creation of Spider-Man, even though Stan Lee is usually given credit. The Fly was the creation of Jack Kirby and Joe Simon and the first successful Silver Age superhero of Archie Comics. He first appeared in The Adventures of the Fly #1, August 1959. Even then, The Fly may not have been an original creation. According to Kirby, earlier in the Fifties Simon and Kirby had created a similar character called The Silver Spider for Black Magic, a title published by Crestwood Publications (who also published Kirby and Simon's Fighting American). For whatever reason, the character was not published. Jack Simon disagreed with Kirby's account, saying that The Silver Spider was originally called "Spiderman" and was not created for Black Magic. The name was later changed from "Spiderman" to "The Silver Spider." The one thing that Simon and Kirby both agreed upon is that when Archie Comics had hired Kirby and Simon to create new characters for the company, they dusted off The Silver Spider and reinvented him as The Fly.
Of course, Stan Lee's account of the creation of Spider-Man differs from that of Kirby and Simon. According to Lee, he was inspired to create Spider-Man by the pulp hero The Spider. He also said that he was inspired to create the character by by seeing a fly climb up a wall. Steve Ditko claims that Lee liked the name "Hawkman" from DC Comics and that the hyphen was added to Spider-Man's name to avoid confusion with Superman.
Regardless, The Fly is remarkably similar to Spider-Man. That having been said, The Fly was also similar in some respects to Captain Marvel. Tommie Troy was an orphan hired by Mr. March. One night while in March's attic, he found a fly shaped ring. Placing the ring on, Tommie inadvertently summoned Turan of the Fly People. The Fly People had chosen Tommie to be their champion and granted him the ability to become the superhero The Fly. All he had to do was say "I want to be The Fly' and he would be changed into the adult hero, The Fly, endowed with the powers of insects. Not only does Spider-Man's spider powers resemble those of The Fly, but it must be pointed out that the two both started out as young boys (although Spider-Man was a teenager at the time of his origin). Whether Spider-Man was, as some insist, a plagiarism of The Fly or whether Stan Lee developed the character independently, the two are remarkably similar.
The same accusation as been made with regards to The X-Men, which some believe was a plagiarism of DC's Doom Patrol. The Doom Patrol first appeared in My Greatest Adventure #80, June 1960 and was created by Arnold Drake and Bruno Premiani. The Doom Patrol was a superhero team assembled by a genius in a wheelchair known only as "The Chief." They were also outcasts whose super powers had left them rejected by society at large. While The X-Men resembles The Doom Patrol in that both are teams of outcasts assembled by a genius in a wheelchair, it must be pointed out that The X-Men first appeared in Uncanny X-Men #1, September 1960. With only three months separating the debut of the two teams, there would not have been sufficient lead time for anyone to have plagiarised the concept behind a new superhero team, written the first issue, and seen it published. Quite simply, the resemblance between the two teams is most likely a great coincidence.
Regardless, in some respects the powers of some members of The X-Men are not particularly orignal. Cyclops' ability to produce optic blasts from eyes was one of the powers possessed by an MLJ (now Archie) character called The Comet. Created by Jack Cole, The Comet debuted in Pep Comics #1, January 1940. The Comet was a young scientist who gained the power to fly and to emit rays that disintegrate anything from his eyes. He even had to contain the rays with a special pair of goggles, much like Cyclops. The Comet did not have a long run and is probably best remembered for being the first superhero ever killed. In Pep Comics #17, July 1941, gangsters murdered The Comet after he put their boss in prison. His brother became The Hangman to avenge him. The Hangman proved a bit more successful, lasting until 1944. As to other members of The X-Men, Iceman was obviously a reversal of The Human Torch, generating ice instead of fire. The Angel, who had wings that actually work, obviously owes something to the Golden Age All-American (and later DC) character Hawkman.
Here I must stress it not my intention to make Stan Lee out to be a plagiarist. While the powers of his characters may not have always been original, his treatment of them was. Before The Fantastic Four's debut, it was rare that comic book characters had problems that people in real life do, or even had flaws. This was then largely a revolution started by Lee. It must also be pointed out that by the end of the Golden Age there had been so many different superheroes that it was probably very difficult to develop a new character who did not have powers that had been used for a superhero before. It must be pointed out that the bulk of DC's Silver Age characters were new versions of Golden Age characters. It was not until the Sixties (many years after the introduction of the new Flash) that DC saw any characters with original powers, such as Metamorpho (introduced in The Brave and the Bold #57, January 1965) and Deadman (introduced in Strange Adventures #205 (October 1967).
And while various characters created by Stan Lee may have not been particularly original in their powers, he created others that were starkly original. While The Hulk owes a great deal to Dr. Jekyll and Mr, Hyde and Frankenstein's Creature, it was the first time that the idea of a normal man transforming into a monster was used for a superhero. Iron Man was even more original. He was the perhaps the first superhero whose powers were derived from powered armour. While many of Lee's characters did not have particularly original powers, this could be said of many comic book creators after the Golden Age. And Lee showed more than enough originality in the creation of characters like The Hulk and Iron-Man and in giving his heroes flawed personalities.