Have you ever argued for your best teacher? “Mr. A was the best!” and your friend says “Oh yeah! And in college I remember Ms. B teaching me the most.”
Perhaps you may have debated who was greatest among classic philosophers: Socrates, Plato, or Aristotle?
It’s a fun debate, and I’ve revealed my choice earlier. But here, I can provide us with an objective measure that we should all be able to accept. It has some shortcomings, but every measure has benefits and drawbacks.
The greatness of a teacher should be measured by how many subsequent teachers they create.
You see, it’s not necessarily important that they teach something totally awesome, although it doesn’t hurt. It’s not even important that we be able to understand what it is they did.
With respect to philosophy, Socrates taught Plato.
Plato taught Aristotle.
Aristotle taught, hmmm, who did Aristotle teach? I heard that he taught Alexander the great, but Alex wasn’t exactly known for being a good teacher. He was more of a doer.
There we have it for philosophy. So Socrates is the greatest teacher among them. We can debate which of them had the “best” philosophy  but that’s for another day.
How about something like physics? Archimedes is easily the first in this category, both theoretical and experimental, but we don’t know if he left any teachers behind. Tycho Brahe was a polymath that included physics, he taught Kepler, and Kepler taught Newton. Who did Newton teach? No one directly, as far as I know. He did teach many indirectly, but I’m not counting that.
Einstein is one of those people who learned from Newton, Faraday, and many others. But did he teach anyone? Not sure.
So, are Archimedes, Newton, and Einstein still great scientists? Of course. But were they great teachers?
My measure says no. Is that worth anything?
Now that is something we should discuss another day.
 Socrates, with Plato being a close second. Archie was a hack who sold out for celebrity.