Well, Frankel The Wonder Horse got it done at Ascot, didnee?
Workmanlike rather than imperious, most spectators agreed. Fourteen straight victories, no defeats. A great horse, for sure. But the greatest ever? Not for me. The greatest horses win the greatest races - in Europe the Derby and the Arc de Triomphe, in the U.S. the Triple Crown, and nowadays The Breeders Cup Classic.. Frankel didn't. So he's only potentially the greatest. Sea Bird was the greatest European, Secretariat America's greatest - whose 1973 Belmont Stakes win must be the the most amazing performance by any horse, any time, anywhere. Ever.
(You can see it on Youtube, anyway, if this doesn't work.)