Now that I pissed off as well the fans of the series, as the ones of Asimov, let me explain:
Asimov set milestones for SF:
His Laws of Robotics and Foundation are cornerstones of the genre.
When I say: "His literature is mediocre" it's because he is not truly interested in his characters. He has no love for them. His stories are ideas driven, not character driven.
I'd still recommend him to anybody, even mildly interested in SF.