[William Cloud Hicklin]

In terms of "moderns" with a high degree of intellect and literacy, E.R. Eddison's (not Harlan Ellison's!) The Worm Ouroboros (1922) rates very highly, as does David Lindsay's Voyage to Arcturus (1925; a challenge to read, in places nearly as dense as Joyce). Also, although IIRC also unknown to Tolkien, Peake's Gormenghast (1939). William Morris was a profound influence on Tolkien, especially The Roots of the Mountains, The House of the Wolfings, and his version of Sigurd; he also serves to demonstrate how elegant Tolkien's archaizing style really is compared to Morris' labored Victorian tushery!

Brilliant but utterly un-Tolkienian is T.H. White's The Once and Future King (1954).

Then of course there is all the ancient material: especially Beowulf (personally I prefer Tinker to either Heaney or Clark Hall) and the Volsungasaga, as well as Snorri's Prose Edda.

Indispensable also is Malory: as a matter of personal taste I think Caxton's edition is an improvement on the Winchester MS text.

Post-Tolkien there isn't a whole lot. Ursula Leguin is a brilliant author, but her best stuff is scifi rather than fantasy. Gene Wolfe (who corresponded with Tolkien as a young man) is very good in a wierd, hallucinatory way; but his mytho-historical work like Soldier of Arete is to me better than his fantasy New Sun series.

Of contemporaries, George R. R. Martin is about the only one I have time for, and he's basically mind-candy: a sprawling soap-opera episode of Dallas or Dynasty, with bloodshed. (A separate case is Guy Kay, whose one foray into high fantasy, The Fionavar Tapestry, isn't all that good, but whose quasi-historical novels are very good indeed).