I don't doubt ERBs personal success, or his heirs's. I look at it more from an idealistic intellectual perspective, and am annoyed that his name is never mentioned on the listings of fantastic fiction authors discussed on the "high brow" weird-fiction forums. 

Who the hell should care that his prose style is not "fine" literature?! Or that it contain some generic romance and adventure, when still, his daring unhampered ideas and colorful visions present pure archetypal wisdom, that make many "finer" writers's strained compositions by comparison appear bland and irrelevant hogwash?

H. P. Lovecraft, in his younger years, hailed Burroughs, but when he grew older and immersed himself completely into the dark world of "fine" weird fiction,  he no longer mentioned Burroughs, except degradingly. Lovecraft's influence may be part of the reason why Burroughs is never mentioned among the weird fiction "high brow" crowd.