Overrated?? Asimov wrote over 500 books, both fiction and nonfiction. His stories were between the covers of all the science fiction magazines every month. And the trilogy you rate so poorly won a Hugo award (the most respected science fiction award there is, with the possible exception of the Nebula). He, Heinlein, and Clarke are are often considered to be the "Big Three" of science fiction authors.
Sheesh, judge the author of over 500 books on three. That's pathetic.
Oh, and in case you didn't figure it out, I've been a huge Asimov fan for fifty years (as well as Heinlein and Niven and most of the rest). I didn't care for Clarke, but I'd not call him unimpressive, I just didn't care for his style. If I cared for that style I'd probably love his work, but I don't.