The greatest heroes of their respective worlds, there are numerous points of comparison between the Supermen and Captain Marvel. However, it should be noted that both Earths One and Two had their own Billy Batson, albeit each was powerless. On Earth-S, Billy's alter ego of the Captain was a separate entity, as each spoke to the other as individuals numerous times. Interestingly, the Earth-One Superman had a separate career as Superboy and was in fact a separate person from his older self due to the machinations of Pete Ross and later Lord Satanis. Over on Earth-Two, that Superman had a "twin brother" in the form of the hero Doctor Occult, who even had a costume like his with a reverse color scheme... as well as powers to match. For Marvel, his progenitor was Teth Adam aka Black Adam, who was heroic for a time before turning towards evil. Like the Doctor, Adam was empowered in Egypt to save humanity which he did for a time.
While the first and foremost protector on their planets, these men manifested singular courage and conviction unmatched even among their noble peers of the day. As to their similarities:
- Their powers included superhuman strength, superspeed, flight, invulnerability, astute senses, vast intelligence.
- While the Supermen had heat vision as an outlet of energy, Marvel had his lightning bolts which he used on occasion in battles.
- Each wear costumes consisting of flowing capes, defining chest emblams, and red and yellow in their color scheme (Cap missing Supes' blue, however).
- As youths these heroes were orphans who were later adopted or overseen by kind elderly couples.
- In their civilian identities they were journalist, with Earth-One's Clark Kent joining Billy as a televised newsman.
- After becoming legends, they met their long lost females who were their closest living relatives and epic heroines.
- Their arch-foes were fiendish scientists, as well as having unliving duplicates made of all three of them.
- The cities that hosted this triumphant triad, the Metropolis of Earths One and Two and Fawcett City of Earth-S, were legendary.
- Each was a founding member of his world's leading team of superheroes, and inspired generations of other champions.
And this is just scratching the surface...