Edgar Rice Burroughs certainly, as also Jules Verne.
L Neil Smith would be in a personal list, as well as Dean Ing.
RAH didn’t think to highly of A C Clark if memory serves...
Maybe the “top” list should be longer.....
.02,
KYPD
While he does push my Libertarian-leaning buttons, he's too one-dimensional of a writer to be on my personal list of top authors. Talk about wearing your politics on your sleeve...!