Okay, I simply have to jump in here with my two cents' worth:
First, it is wonderful to come across some people who are into intelligent discussions on such a topic -- even the ones I disagree with sound refreshing! I hope I contribute something as worthwhile.
Now, a few general comments on the prior posts: Machen was concerned with "illuminating ecstacy", which makes his stories often rather confused and pointless as far as plot goes (not to mention heavily loaded with extreme coincidence); but his use of the language and ability to convey a subtle drifting from the "common reality" into another realm where spirit rather than flesh really was the important thing (he maintained an almost medieval Church view on the topic) is definitely hard to surpass. He's subtle -- at his best -- but if one reads him in a receptive mood, he can weave quite a spell.
Good to see Crawford mentioned, his "Wandering Ghosts" has recently been reprinted here in the U.S. with additional material left out of the original edition. I'd still say "The Upper Berth" is among his finest, even if it has been overanthologized.
There are some facts coming out about Bierce that rather challenge the standard view; some recent bios and collections of much of his long-neglected writings (essays and such, not fiction) are starting to change the image of "Bitter Bierce" to some degree. But it probably is correct he died in Mexico in 1914 -- if he got near enough, he probably broke his cane over Villa's head; he didn't have much patience with those he thought fools.
I'd love to discuss others, and if anyone else is willing, let me know. As for HPL -- hmmmmm! I suppose it's a matter of whether you like "Asianic" prose or "Attic". His old-fashioned style was more a product of reading the 18th-century essayists (Addison, Steele, Johnson, Gibbon, etc.) and 17th/18th century poets rather than fictionists, with the exception of Poe. And he uses many poetic techniques in his stories to weave the atmosphere, as well. Not for those into fast-paced stories (though the chase in "Shadow Over Innsmouth" certainly shows he could do such), but I can't agree his style was at all bad; simply not something we've been used to since the turn of the century (although some of ERB's books, when you read them, are incredibly dense stylistically; not to mention Abe Merritt).
At very least, I hope some of my comments spark more responses. This could be a great deal of fun (then again, I seem to have a peculiar taste; as my boss used to say: "You really like the weird old sh*t, don't you?"
I look forward to others' comments; and I repeat, My God, this is refreshing!