When I was young, I wanted to change the world. Like most people, I thought that the right way to do this was through politics, or working for NGOs, or in the world of policy. Nowadays I tend to think you're doing well if you're able to make things better for your own family and local community at the most. But I also increasingly think that when we talk about 'changing the world' in common parlance - particularly when we're young - we unduly privilege politics. Of course, politics matters. But humans are spiritual beings. You can change the world by creating things that uplift people's souls and make them glad to be alive - that give them the opportunity to step outside of themselves, to reflect, to imagine that there is more to the world than just the mundanity of doing.
I don't mean that this makes the world better in just some airy-fairy artistic sense, although uplifting people's souls and making them glad to be alive is intrinsically good in its own right. I mean it in a practical sense too: when people are uplifted from time to time, they live fuller, richer, more productive and interesting lives, and this cannot but contribute to a better society overall. We can't measure this quantitatively (like we can't measure most things that matter quantitatively) but you only have to think about the issue for a moment to realise that a society in which public morale is lifted by having access to inspiring and wonderful art and entertainment will be healthier, happier and more secure, as a consequence of being spiritually better off, than it would otherwise be.
It sounds awfully pretentious and trite - as well as ludicrously precious about the value of one's mere hobby - to say that on these terms Gygax and Arneson changed the world considerably, just as did Dickens, Camus, Tolkien, Hemingway, Gaugin, whoever else you wish to name. No, mentioning them in the same breath as Gandhi or Martin Luther King or Lyndon Johnson or Margaret Thatcher would be silly. But the cumulative effect of their game diffused and spread among the millions of people around the world who have derived satisfaction from it and its progeny is not, in terms of the public benefit, nothing. It isn't just a game (although that in itself would still not, of course, be nothing).