I am of the opposite opinion that circumstance takes a huge part in the creation of greatness, greatness might even be an accident in most cases. I dont think it is written under the stars that someone is going to find his way, circumstances have to be precisely right for most players to dominate the tennis world, right opponents, right surfaces, right raquets.
I can understand your point, but I still think that players like Connors or Sampras would be great during any era. They would make adjustments and they were mentally champions.
While we can't have a time machine, we have to have a tournament where the guys play with wooden rackets and the kit from the 30's. Who would win? I could see Brands doing some incredible stuff.