The Mozart thing relates to an ex-boss, who had probably forgotten more about classical music than I'll ever know. He had no time at all for Mozart, who, he said wrote nice tunes but 'you always knew what note was coming next'. Bach, on the other hand, he regarded as a genius whose work would never be surpassed. But, yes, most people would put Mozart at or near the top of the tree.
With Dylan, I think it's the combination of words and music. His lyrics don't stand up as poetry, and his voice is nothing to write home about, but put them together and, for me at least, his work is up there with the best. Plus, he moved music along, for better or worse.
So, undisputed geniuses. In their different fields, maybe Homer, Euclid, Pythagoras, Leonardo da Vinci, Shakespeare, Newton, Bach, Mozart, Beethoven, Goethe, Einstein. All men, all white, all European.
My knowledge of maths and science is scanty so I'm sure I've missed some obvious candidates, and I'd be wary of classifying philosophers. Is there such a thing as a sporting genius, or a genius in the performing arts, where memory of performances have a relatively short shelf-life?