Arthur D. Hlavaty

Having spent four years at Harvard back in the day, I can say that big-name professors are not necessarily the best teachers. Not a few of them seemed unable to communicate well to anyone under the Ph.D. level. Their reputations come from their research and their writings after all, not their teaching.

That said, I had some professors at Harvard who were excellent teachers; two were assistant professors who, in defiance of the usual tradition that Harvard never grants tenure to assistant professors, went on to get tenuted positions; one, a specialist in the Qur'an, ended up dean of the Divinity School.

I've read that Tolkien was a professor of Anglo-Saxon whose happiest moments were spent with C.S. Lewis and some others reading Old Icelandic sagas out loud to one another. It wouldn't surprise me at all if he were not the greatest teacher.