I'm comfortable with the Healey/McComas 1939 - 1945 recommendation. Doyle and Wells seem completely modern to me --- make that better than modern. ERB is better than a lot of people give him credit for.
That calls for a response -- to which books would you refer sf/fantasy readers as being his best? (Why?)
It's not an entirely idle question. Last year I revisited ERB a bit, not having read any of his books since I was about 15 (but at around 14-15 I read the 11 Martian books, the Pellucidar books, the Caspak books, the Moon books, Beyond the Farthest Star, The Outlaw of Torn, The Mad King, a few Tarzans I suppose... some of these more than once). I found At the Earth's Core entertaining but bogged down about halfway through A Princess of Mars.
I think my first ERB book was probably A Fighting Man of Mars, the sight of the Ace cover of which
brings back quite a sense of the lad I was over 40 years ago!
I don't know what his best books are but I had no trouble with these:
Good solid adventures. I was especially impressed with THE MONSTER MEN. The ending caught me so by surprise it took both my thumbs up to put my jaw back in place. Your cover, by the way, is stunning. I'd love to have all the John Carter books in those forty cent editions.
Btw, I've been reading Michael Dirda's On Conan Doyle. If you like those "Golden Age" authors for sf and fantasy ... so does he, so you would probably like borrowing this book. Doyle, Haggard, Dunsany, Burroughs, Wells... he's read 'em, although he doesn't necessarily say a lot about all of them. Mentions Lovecraft, Howard, and Tolkien too. Not bad for a book published by Princeton University Press.
I'm finding it easy to reinforce your argument, Extollager. G. K. Chesterton's The Man Who was Thursday and his collection, The Innocence of Father Brown (since Sherlock Holmes was mentioned) were published within this time range (1908 & 1911, respectively). As was Max Beerbohm's Zuleika Dobson (1911; unfortunately, "Enoch Soames" misses by 4 years, 1916, darn it). (Also, darn it, The Strange Case of Dr. Jekyll and Mr. Hyde just misses -- 1886.)
Following up on something you mentioned, Arthur Machen's "The Great God Pan", "The Inmost Light" and The Three Imposters (1890, 1894 and 1895, respectively), and Algernon Blackwood's "The Willows" (1907) and "The Wendigo" (1910) appeared in that time.
Other books to appear in that time period, Tales of Soldiers and Civilians (1890; including "An Occurrence at Owl Creek Bridge") by Ambrose Bierce Can Such Things Be? (1893; mainly weird horror like "The Damned Thing") by Ambrose Bierce (some stories written before 1887 in both collections, but the collections post-1887) The King in Yellow (1895) BY Robert W. Chambers The Picture of Dorian Gray (1891) by Oscar Wilde The Ape, the Idiot, and Other People (1897; includes "The Monster-Maker) by W. C. Morrow
Much Decadent literature, like the Wilde, showed up at this time, like La-Bas by J. K. Huysmans (1891). As did The Beetle (1897) by Richard Marsh, which is said to have been more popular for quite a long time than its contemporary, Dracula. Also, Turn of the Screw (1898) by Henry James.
Note that during that time period, the short story was probably more important to ghost/horror, s.f. and fantasy than the novel. With today's novel-centric point of view among readers, that fact can be lost, but stories like "The Willows," "The Great God Pan," "An Occurrence at Owl Creek Bridge," "The Yellow Sign" and "The Monster-Maker" all are part of the foundation on which contemporary sf/fantasy/horror are built. I'm positive, with just a little more digging, I could come up with some other titles/authors, perhaps more obscure, but still important to the development of these genres.
Ew! Tough call, but I think I'd have to go with 1950 to 1975. I have to include the '50s, in part because of literature, but also because I've often asserted that th 1950s' sci-fi movies rocked. We were gaining enough scientific knowledge to make the premises believable, and yet not enough to understand yet what won't work. It was spectacular in those days.
At the other end, I have to reach to 75 to include such classics that will stick in my head forever such as Mote in God's Eye, Ringworld, The Andromeda Strain, and Rendezvous with Rama. Rendezvous with Rama