The concept of half-elves, perhaps, but not the implementation. D&D half-elves are far more common than in Tolkien, where there were, like, five of them ever. Also, D&D half-elves are midway between elves and humans in stats, while in Tolkien, they are physically indistinguishable from elves as far as we know but just potentially go to a different place when they eventually die (depending on what decision they make about that).
On the last point - Elros was not physically indistinguishable from elves, but rather chose to be human. I'm also not sure about Earendil - as a half-elf was he more evlish or human?
In any event, it's true that D&D's implementation of half-elves is different from JRRT's but that's true of most elements. All 10th level rangers, even the King of Keoland, can use palantirs. Nevertheless the derivation from JRRT is pretty transparent.
And there is nothing stopping a particular table treating half-elves as rare, or the ranger class as very distinctive - much as a GH campaign would be expected to treat open-hand monks.
pemerton said:
But GH needn't be limited to Tolkien, and in many ways is not well-suited to it because evil in GH is somewhat diffuse rather than all the result of the Fall.
If anyone said it should be, I missed it.
There was at least one post upthread which suggested that GH should be confined to "traditional" fantasy races (by which seemed to be meant JRRT + gnomes). I am disputing that claim. I think that GH as a setting has ample room for non-JRRT humanoids, and that the issues with playing (say) a dragonborn are no different from those with playing (say) a valley elf or an open-hand monk.
Gary didn't really care for LOtR. He liked The Hobbit far better. He also didn't like Magic Users. I think this is pretty well known
What's the basis for saying that Gygax didn't like MUs. He played them (eg Mordenkainen).
rules-wise he was going more based on Earth mythology, and not Tolkien mythology
I agree with
@Doug McCrae's post not too far upthread. But I'm also not sure what the contrast is you're drawing between Earth mythology and Tolkien mythology - JRRT's material is drawn from traditional folklore, but treated and developed in a way that tries to make sense of it within the context of a 19th-century style novel rather than the earlier feel of stories like Beowulf, Sir Gawain and the Green Knight, etc.
That said, D&D is much better suited to playing JRRT-type fantasy than much mythology. Eg I think it's quite hard to play an Argonauts or Iliad game in D&D, because martial PCs aren't presented in the right way for that. Which is a legacy of the game's wargaming heritage.