It depends on what you're truly asking. I don't think either of them could comprehend something that the other two couldn't have. That being said, I don't think Einstein or Hawking were capable of inventing calculus, which is pretty much exactly what Isaac Newton did, as well as lay the groundwork for physics. Newton is, in my opinion, the most intelligent man in history. Without calculus and Newton's laws there would be no scientific breakthroughs for Einstein or Hawking. If you really want to see exactly how smart Sir Isaac Newton was, take calculus I, II, and III, then tell me Einstein is smarter.