One might say that Science Fiction is an acquired taste. The field is not as exploitative or sappy as romantic storywriting. The number of authors who have made it in SF is actually small, when you think about it. Every one of the writers in Silverberg's anthology, Science Fiction Hall of Fame, Volume One, 1929–1964, is well known to me.
http://en.wikipedia.org/wiki/The_Sci...9%E2%80%931964
Certainly Asimov belongs in the same class of writers as Heinlein, del Rey, Bester, etc. Isaac may not be in the same league as Sturgeon, but, that is a matter of personal preference. Because SF does not aspire to the lofty ideals of
great literature, the average fan is satisfied with a good plot and mild amusement. SF was not haute cuisine, nor was it nouvelle cuisine. That was the credo Asimov followed, and who can blame him? Was the world ready for esoteric, new wave Sci Fi when he was writing? Yes, and no. Thomas Disch was brilliant and ahead of his time. But not in a commercial sense, meaning he never raked in the big bucks like Asimov or Bradbury. Possibly, the operative word was
accessible. Drift a little, but not too far afield. If China Mieville were writing in 1950, he would have been shunned. Incomprehensible, way too avant garde. Could Asimov have altered his writing style over the years? Not after he tasted fame and publicity. That would be like asking Stephen King to pen The Brothers Karamazov. Rather than critique Asimov for what he wasn't, let's just say there are many writers in the universe to read besides this one man. Asimov is neither overrated or underrated. After all, he did not get a Nobel prize, did he? Try other authors, even Doris Lessing. No comment on her. Why? Because it takes a lot of reading to tell how good or important a writer may be, in his/her lifetime.