JRR Tolkien is hailed as the forefather of fantasy fiction, especially when it comes to epic fantasy and the like. He pretty much created the blueprint for modern fantasy fiction, often with a feudal feel complete with dwarves, elves, orcs and hobbits. While not all fantasy works contain any one or more of them, it’s apparent with fantasy brands like Dungeons and Dragons and Warhammer Fantasy as well as Warhammer 40K. But his friend and colleague CS Lewis didn’t leave much of an imprint on subsequent fantasy works, well not to the extent JRR Tolkien has done for so long. In part because some of his biggest fans were Christians, I guess that’s got more to do with seeing the fantastic in real life when it comes to miracles, answered prayers and prophecies.
These are big in Christianity, especially among the more pious. I personally feel when you do see the supernatural in real life, be it angels, demons or witchcraft this is probably the reason why you don’t see that many Christians doing speculative fiction much. If because to them, real life is already fantastical if you take these things seriously. Witches aren’t speculative superhumans, but rather truly dreadful as it was reflected in folklore before. I guess when it comes to Christians seriously believing in miracles and the like, this is possibly why CS Lewis’s influence on secular speculative fiction seems rather limited. Nonetheless, he did make an influence on some secular productions like Digimon for instance.
Not that CS Lewis didn’t influence fantasy and the like at all, but that much of his influence is more greatly felt among Christians than it is among non-Christians. Tolkien’s work seems more palatable for secular readers, since the Christian themes aren’t so blatant as it is with Narnia. That’s why he seems more influential in fantasy literature, especially when it comes to things like Dungeons and Dragons and Warhammer Fantasy.