Do you know the name of the person that invented the Internal Combustion engine, without looking it up?
Do you need to look up who Henry Ford is, or Elon Musk?
Being relevant to an emerging market is being part of "living history".
Being an unknown figure to that emerging market means being relegated to the footnotes of history.
Outside the Against the Giants conversions in the Yawning Portal...there is not much of Gary's world building in 5e. Hopefully that will change in 2021..
I have never needed to know who invented it, so no, I could not tell you without looking it up.
I'm quite aware of who Henry Ford was, and why his car company (which still bears his name) is historically relevant. I could even tell you how his changes ultimately derive from the concept of replaceable parts, particularly the work of Eli Whitney during and following the American Revolution.
Elon Musk is currently a rather famous person, so I'm not really sure that was a great example. He's the CEO and chief engineer of Tesla motors and SpaceX.
None of these points, however, make up for the fundamental problem of your argument: the question
asked by the poll is, "Whom has had a greater impact on D&D?", but the question you keep
answering in your posts is, "Who is more relevant to current gamers?" Your talk about being "relegated to the footnotes of history" and who gets to be involved in "living history" simply reinforces this; you are, as I said, conflating historical importance with current-day relevance.
If you wanted to ask about relevance, you really should have made that the question you asked--and I'm pretty sure you would have gotten more interesting, and less lopsided, answers as a result. Instead, you asked whether one of the game's creators, or someone who contributed a popular setting, has had more impact, and most responses have quite reasonably said, "Well, seeing as how the game could not recognizably exist as it does without Gygax but could recognizably exist as it does without Greenwood, Gygax is more impactful than Greenwood."
I cited Euclid for a reason. He isn't necessarily all that relevant to the way we do geometry or mathematics today. The ancient Greeks, for example, did not think of "numbers" the way we do, they thought of
measures, and how measures could span one another. Euclid did not prove that there were "infinitely many prime numbers," because "infinitely many" wasn't a concept for the math of his time (and would have been deeply troubling to them); instead, he proved that any fixed and finite set of measures (for which a unit measure has been defined) cannot possibly contain all measures which can only be spanned by themselves or the unit measure. This is awkward and cumbersome by modern standards, so we rarely use Euclid's proof directly, often translating it into modern terms like numbers, formal sets, infinitely many things, etc.
In many other ways, the geometry of Euclid has often been superseded by more refined or developed techniques, such that it is not necessary to ever hear his name or read his work to learn geometry from the Western tradition. And yet it is still true that if you picked Euclid and any mathematician currently alive, almost all experts in the field would tell you that Euclid had "greater impact" than the challenger. The only people who could even potentially challenge for the title would be those like Riemann, Gauss, and Euler--people who actually DID invent or reinvent the "game" itself, rather than contributing small iterative steps. And wouldn't you know it, we get names like Williams, Moldvay, and Cook in the thread. If you had said Monte Cook (not to be confused with the previous Cook), you might even have gotten some traction, because he was very important for 3e's development and the rise of D20 gaming.
Greenwood though? The man is primarily an author. It would be like comparing Shakespeare and JK Rowling and asking who's had more impact on modern literature. Of course Rowling is more famous, but Shakespeare heavily defined our modern language even if we don't use it today the way he did then. Relevance and present-day awareness are entirely orthogonal to historical impact.
Impact =/= Current Usage, and Importance =/= Modern Awareness. Acting like the four are all equivalent is counterproductive.
Edit:
Alternatively, if you specifically wanted to discuss worldbuilding, again you should have just said so. It would probably be a more interesting and far less lopsided discussion if you had! We still use many dungeon concepts Gygax did, but as you've said, with much more "heroic" and "high fantasy" trappings like what Greenwood uses. Yet by that same token, we continually return to the classics like Keep on the Borderlands or the Village of Hommlet (remember that one of the early 5e adventure products was ToEE), so it's hard to say that Gygax has ceased to exert creative influence on the campaigns of today.
