With the rise in popularity of ultramarathons, couldn't you take the best time of the 100+ mile races and compare that to times for horses on similar distances

With the rise in popularity of ultramarathons, couldn't you take the best time of the 100+ mile races and compare that to times for horses on similar distances and terrain? When I saw the heading, I was convinced at the end it would say that on distances of 200 miles and longer that those few humans who do actually run these distances have better times than the best horse times...