I think the mistake you're making there is presuming that people like Aristotle are representitive of the average person of their era. That's certainly not the case. Peoples who's names are still remembered and revered thousands of years later are anomalies. The Aristotles of the ancient world represent the best humanity had to offer over a thousand year period. Comparing them to an average person of today is apples to oranges. Instead compare to the most prolific thinkers of the last 1000 years. How does Aristotle stack up against Leonardo Da Vinci or Isaac Newton?