Isaac Asimov for me. I think that his work will not just be regarded as staple sci-fi novels (the way it is today), but as a cautionary and prophetic work, especially with regards to "Psycho-history". He was also a great intellectual role-model who was very outspoken about rationality and optimistic about the ability of youth to learn and curate their interests outside of the boxed environment of standard education.
At the end of the day though, all heroes are polished and elevated above their flawed humanity as time goes by - they become architypes more than actual people, and I believe Asimov will be one of them.