Dark Horse, in conjunction with Sequential Pulp Comics, has just issued a marvelous graphic novel adaptation of At the Earth's Core. Pellucidar, and David Innes, are suddenly alive in ways that they have never been before.
When Kirby and Lee introduced the X-Men to the world, they did so without recourse to that staple of the superhero genre, the origin story. That doesn't mean that the mutant superheroes arose ex nihilo, however. They clearly have roots in these four classic sci-fi novels.