I've done chemistry for a while, starting in 400 level classes as a freshman; then engineering for 3 years - and at the #1 school for that type of engineering, then mathematics (3 more years), with minors in computer science and education along with way, with some grad work in physics, and grad work in education, I think I can say, education grad professors (that I had) - not in my top 100. But, I've run into quite a few very bright people.
So, it's tough to pick the brightest among the professors I've run across. Plus, there are a few colleagues who teach physics at other schools who I'm often impressed with. And, I'd think you'd have to know the person outside their area of specialty to really recognize if all their brilliance is constrained within their field, and they're otherwise not very smart. I.e., they get 30 papers published in a year, but need instructions to put together a kid's toy that contains 5 parts.
If I could go back in time, and meet a smart person, I'd love to meet Richard Feynman & spend a few hours listening to him.