In my book unquestionably Secretariat. I was at the Derby when he won it, and during the following years I had several chances to be very close to him. I might be mistaken but I believe that most of his track records still stand. That was the biggest damn horse that I've ever seen. Huge. Fastest, too.

When they did the postmortum after his death they discovered that his heart was more than 50% largesr than the average first-line thoroughbred. Explained a great deal.