So among the founders of modern fantasy and science fiction, Burroughs seems to get very little respect. Despite starting writing considerably before Tolkien, and achieving much greater commercial success, he is often dismissed as a hack, and with the sole exception of Tarzan, his works receive very little modern attention. Almost all of the great writers that came after him credit him as an inspiration to them, including Ray Bradbury, who called him the most influential author that ever lived.
Yet today, all of his settings are basically unknown, which is a bit weird. Burroughs style of writing was very much adventure pulp writing, but his worlds were beautifully realized and interconnected. It is all very much wish fulfillment, but it is undeniably fun, and it was incredibly popular at the time.
But Burroughs created a lot of modern literary staples. Almost all of his works fit in a vast interconnected universe, that sees the entire solar system populated with human life. Mars is an ancient, arid, dying civilization. Venus is a lush, wild, and chaotic world full of sky pirates and ancient mysteries. The Moon holds caves full of a bizarre and primitive world. Inside the Earth is a fledgling human civilization struggling against the Ice age creatures and an ancient reptilian civilization. And of course the Earth itself is full of lost civilizations and unknown jungles. In many ways this universe was simply the codification of a 1910s era view of the universe (Unfortunately, complete with racism), but it also was incredibly influential on generations of writers that followed, and remains an incredibly entertaining universe to this day. I read almost all of his books as a kid, at least the ones I could find.
But today for some reason nobody gives any respect to the OG Fantasy universe that spawned the ones we have today, and I find that strange. Disney tried with John Carter of Mars, but that movie was a massive flop, partially because it could decide if it wanted to pander to audiences that knew the setting, or pander to those that had never heard of it. Hollywood cranks out lifeless Tarzan movies every couple years like clockwork, but all of them lack the adventure of the originals, and are never connected to any of the key elements of the setting. Still, Tarzan is the only element of his works that is currently known at all. Pellucidar in particular has an enormous amount of potential, yet never gets approached.
So why don't more games or modern works draw from this universe? It is vast and detailed universe that was once incredibly popular. It really isn't hard to cull the 1910-1920s racism and misogyny out of it, and it is old enough that most of it is now open source.