At least these are the favorites Margery Allingham listed in correspondence with Fred Dannay, of Ellery Queen fame ("not in order of merit but just as I think of them"), as tweeted by Sarah Weinman:
John (Dickson Carr)
Erle Stanley Gardner
Mabel (MA struck out "Katherine," written first) Seeley
H. C. Bailey
And, she added to Dannay, "you and me of course!"
Interesting choices, in that the newest writer in the group, Mabel Seeley, had published her first mystery, The Listening House (discussed below), over a dozen years previously. A pretty orthodox list on the whole! After a seven-year hiatus from crime fiction, Seeley has just published her sixth mystery novel, The Beckoning Door, in 1950.