Since you invite discussion of authors in all genres, I will propose Madison Jones as my choice of an author who received some recognition in his lifetime but who has become unjustly obscure.
http://www.sffchronicles.co.uk/forum/538937-madison-jones-1-an-exile-i-walk-the.html
I'm going to start today a rereading of novel A Cry of Absence, which, a few years ago, was the first novel by him that I read.
Indeed I did say all genres. I did bring up Norman Douglass who wrote South Wind which both he and his books were celebrated at one time
Also Cornell Woolrich He gave us such great books as Night has a Thousand Eyes , Rendezvous in Black , The Black Angel and so many other wonderful books. He was very prolific and popular in his day .