One has to wonder how the greats would match up. Who would win a race of Man-O-War, Secretariat, Seattle Slew, Affirmed, Unbridled, the other great horses? - you can't really compare them by time... as their speed would be influenced by the speed of the others in the race at the time.
What do you think? - Are the horses today faster than those of the past? Have they been improved even more? - or not? Is the thoroughbred of today pretty much the same as it was in 1917?