Who wins this battle on the best night of both gentlemen's career? Caracas Foreman imo was better than Kingston Foreman, mostly because he shortened his punches.
So 91 Foreman vs 90 Douglas? Ok. I will go with Douglas. He is tall enough, quick enough and smart enough to stay away from Foreman. However, it is a big IF. Douglas's tendency to spam uppercuts worked vs Tyson but Foreman will pick up on it. And at some point, Foreman will either throw a huge left hook or a big booming straight right over Douglas's uppercut and badly hurt him. If Douglas sticks to jabbing and throwing fast 3-4 punch combinations and only ocassionally using the uppercut, he wins a decision. If he gets overly uppercut happy, he gets stopped.
The best version of George Foreman would have knocked out the best version of Buster Douglas. '91 Foreman would still beat Douglas, but I am not as sure about that knockout.