It's not a question that makes much sense.
Who's the greatest plumber who ever lived? Who's the greatest roofer who ever lived?
While I'm sure there is a plumber out there who invented x, y, z plumbing technique, or who was the head of a successful plumber training institute, nevertheless it is far fetched to call any person the greatest ever plumber, or the greatest ever roofer, or indeed, the greatest ever bike mechanic.
It's a manual occupation. It's not Picasso.
100% wrong. I can't believe this is coming from you. You don't know what you don't know. There is definitely such a thing as "mechanical genius". I have been lucky to witness it in the realm of bicycle mechanics, metal working, and geo technical engineering.