Well, a comparison of riders of different eras is always difficult, the circumstances under which riders would train and race were so much different.

The UCI with their new hour record rules tries to make times comparable at least for that event. The fact that Boardman and Sosenka only just could top Merckx' old mark by a very few meters shows that a rider with the physis of the cannibal would kick ass today, too...
On the other hand, the first hour record in which more than 40km were ridden dates back to 1898... ever ridden a bike of that era?