Great stuff!
So you think, 1970 makes sense as a cut off? Sounds like it as per your post.
I wonder if I should dial-back the end date a few years... 2015? Even further? It's easier to estimate who has stood even a short test of time in influence, etc. looking back at least 5 years or so...
Also, I'm stuck (probably stupidly) on hard-copy, single author story collections, (collection selected or not by author)
(added)
King, Staub, Rice, Koontz, Saul - Do you think these best sellers are also among the best actual writers? Could any of them be nixed in favor of one more critically acclaimed, or highly esteemed by yourself?
Part I - 1900-1935 7 (Machen, Blackwood, Smith, Benson, Chambers, Lovecraft, M.R. James)
Part II -1935-1970 7 (Leiber, Beaumont, Matheson, Bloch,.... (need 2 more of comparable stature)
If it's up for a vote, I'd go with Shirley Jackson and Robert Aickman. Jackson's "The Lottery" is a quintessential American story, at least for its time, questioning the value of tradition; the stories by her I've read strike me as in line with the other writers you've chosen; David Hartwell said she once told him that she owned the complete run of
Unknown magazine. Aickman on the other hand was non-pulp, and not really even genre, a particular literary sensibility possibly in line with an earlier writer like Walter de la Mare, producing stories more like those of de la Mare and maybe L. P. Hartley and Daphne du Maurier than with Bloch, et al.
Two others, Ray Bradbury and John Collier, would also make good choices. I'd almost go with Bradbury over Beaumont, much as I enjoy the latter's stories.
Part III-1970-2015 7 (Ligotti, King, Staub, Rice, Koontz, Saul, (need 1 more of comparable stature)
I think 1970 is okay, but the period stretches a bit far. The horror boom period started roughly in 1967 with
Rosemary's Baby and ended by 1995. In that time period short story writers of note would include King (he is worth reading), Ramsey Campbell (very worth reading), Charles Grant (a favorite of many readers, but I've only found him okay), Dennis Etchison (I've only skimmed the surface of his work), Lisa Tuttle (I'm currently enjoying
A Nest of Nightmares though she's probably not a major figure for her short work), Clive Barker (major figure, especially in his early short stories in
The Books of Blood, but I've read only one story). Peter Straub is more of a novelist, but has written some really good short stories and novellas, like "The Ghost Village" and "Pork Pie Hat." I've read less than a handful of short stories by Thomas Tessier but judging by them and the three novels I've read by him, they would be worthwhile reading. Still, some major figures at the time, I have yet to dive into like David Schow, Chet Williamson, Steve Rasnic Tem, Melanie Tem, Nancy Collins, Richard Christian Matheson (son of the other Richard Matheson), Douglas E. Winter, Christopher Fowler, and on and on.
My interest in horror/dark fantasy started in the early '70s, but my interests were elsewhere by around '82 or '83, so I didn't keep up with the massive amount of horror being produced -- not a bad thing because a lot of it wasn't very good according to reasonable sources. I'm a bit more well-read in the period following 1995.