Some might argue that Gamma World, written by James M. Ward and Gary Jaquet and first published in 1978, is unintelligible outside the context of the Cold War. There's unquestionably some truth to that. Gamma World's inclusion of mutants and radioactive wastelands is definitely a reflection of Western fears of an apocalyptic World War III that would usher in a new dark age more horrific than any we could imagine. Goodness knows that, as a kid, I more or less expected there to be some final reckoning between the nuclear powers in my lifetime.
But I'm pretty sure that's not why Gamma World appealed to me back then. The mutants and the radiation were just window dressing for me, a convenient way to frame what is, I think, a much more primal fascination with the End of the World in a broader sense. Pretty much every human culture that's ever existed has considered itself to be the last one, teetering on the brink of collapse and whose passing will herald the destruction of all that is good and beautiful in the world.
It's a peculiar kind of hubris and I don't deny that, for much of my life, I've convinced myself to varying degrees that the End was just around the corner. Morbid though that conviction may be, there's profit in it nonetheless, at least if it makes one consider what's truly significant about one's culture and what bits of it are hardy enough to survive the collapse of its supporting structures. If this all sounds a bit pretentious and highfalutin, perhaps it is, but the Gamma World games I ran as a younger person were filled with moments when the player characters encountered some vestige of The World That Was, resulting in comedy, darkness, and occasionally awe -- far headier stuff than ever occurred in most of my D&D games.
That's the power of the post-apocalyptic genre, I think: approaching the present day as if it were a lost civilization whose culture and values are utterly alien to us. I've said before that, in a sense, most pulp fantasies are post-apocalyptic fantasies. Many take place in a fallen world after the oceans drank Atlantis and the gleaming cities. Not only does this set-up lend the weight of history to a setting, it also provides an excuse for ruins to be explored and plundered. As a D&D player, I found Gamma World all too easy to wrap my head around. It's a game that's ready-made for sandbox play and where rootless adventurers moving from one pocket of civilization to another makes perfect sense. In some respects, the implied setting of Gamma World makes a fair bit more sense than does that of D&D and it's eminently gameable.
I played a lot of Gamma World once upon a time and have many fond memories of those long-gone campaigns. I still remember a mutant rat PC who died, in a moment I could not have scripted with a straight face, when he ate a container full of Intensity 18 rat poison I rolled up as random treasure from a table in the book. I will also never forget the would-be Knight of Genetic Purity who suffered mutations as a result of exposure to radiation or Davion, the mutant frog, who wore a football helmet and used a shield with arcane word "Yield" emblazoned on it.
Despite my musings up above, Gamma World certainly wasn't a deadly serious game, but I think that was part of its charm. Unlike D&D, I was rarely tempted to run Gamma World completely humorlessly. My campaigns tended to careen wildly between low comedy and high adventure, spiced up by dark meditations on the downfall of our world. Perhaps unsurprisingly, I think very highly of Mutant Future and regularly consider running it as a break from the Dwimmermount campaign. I still might one day.