As I read through old Appendix N works and old pulps, I noticed a very curious pattern, even in the fantasy novels: a near-total lack of superpowered heroes.
Even in the most fantastical settings, few heroes had anything like the panoply of abilities that modern superheroes have. At best, you would have a
John Carter granted a slight power boost by Mars’ lesser gravity, [EDIT (9/2/2017): It’s more than this; see the comment below.] Tarzan with uncanny physical acumen or a Holger Danske knowledgable about scientific things that medieval people wouldn’t be, or a Viking warrior wielding a cursed sword. But nobody in classic sci-fi and fantasy wields some innate enhanced power like a weapon to mow down small-fry villains while clawing their way to the big boss; we know this to be true because works influenced by the classic books, such as the original Star Wars trilogy, the Gorean Saga, and the Redwall series, often did their heroes in this way.
I have a simple theory as to why the classic works were written that way: it is because they were written at a time before visual media came to dominate sci-fi and fantasy.
Before video games, television anime, and superhero films, authors had only one thing to influence them: real life. Even the films and TV of the pulp era and beyond tended toward non-fantastical depictions of life, rather than over-the-top fantasy. Thus, people wanting to write about strange new worlds and unusual vistas only had their own life experience and personal knowledge to look upon, and the authors who influenced them were similarly constrained. Superpowers? Those were for children’s books.
For example, it is clear that the Gorean Saga was written well before the advent of the Japanese video game RPG: Tarl Cabot does not attempt to end slavery on Gor, nor does he try to overthrow the Priest-Kings. Had it been written like an RPG, Tarl would be a teenager, he would have a party accompanying him (inclyding a former slave girl), he would subvert the slavery system at every turn, and the climax of the saga would be a battle with Sarm of the Priest-Kings (and Misk, another Priest-King, would have joined the party.) Once Sarm is defeated, the Priest-Kings’ system of control over Gor’s technological development would be torn down as they learn the error of their ways. In other words, it would be like a stereotypical Final Fantasy game.
Eric John Stark never had to rely on some special ability to defeat his enemies; he could do so under the constraints of normal humanity. Likewise, David Innes relied only on his wits and whatever fighting ability he could muster to get him through Pellucidar. There was simply no context for something like an optic blast or a Kamehameha; pulling out such an ability would have seemed like cheating to get the hero out of a predicament, or fantasizing about steamrolling one’s enemies without a problem.
Perhaps that is the answer; without superpowers, even small-fry enemies can harm the hero. Thus, the hero has to fight intelligently, and if fighting is not possible, use social skills or other knowledge to thwart the enemy. Thus, the hero can be heroic without being some superbeing who can only be stopped by other superbeings.
None of this is to say that modern superpowered fiction is awful; indeed, I write, read, and watch quite a bit of it. However, the way fantasy heroes were written in the past is instructive, and it can make current-day heroes more engaging.