April 18th marks the 85th anniversary of the release of Action Comics #1. This comic includes the first published story of Superman and Lois Lane.
Originally, Superman was imagined as an unstoppable force for good and a champion of the oppressed. This hasn't fundamentally changed, but the scope and scale at which Superman operates in comics and film has expanded to include liberating whole planets and more nuanced takes on what a man of steel can do and not be painted as a villain by the general public.
In many ways, Superman is a combination of traits borrowed from existing popular fiction. Doc Savage had a Fortress of Solitude, The Shadow had dual identities to fight crime, Zorro was out there swashbuckling and in a love triangle of which he was two sides. John Carter of Mars was an alien on Mars whose origins on Earth made him super-human elsewhere.