How many discoveries were lost to mankind, or delayed by decades or centuries, because Newton spent a significant fraction of his life noodling around with Revelations (producing nothing of vaule) instead of doing more productive research?"
I've often thought about these things, too. But I have come to the conclusion that when the time is ripe, the discoveries will be made. I think this for Gallileo, Newton and Einstein. Even without these men the discoveries would happen, probably by the combined works of many, but still made. Calculus was invented by Leibnitz and Newton simultaneously. His laws would have become obvious, eventually. Gallileo's works had roots in several other's. Someone would have made these discoveries if they hadn't existed.
Einstein, I think is the greatest, simply because there was incredible pressure and competition 100 years ago. He was the one with the vision to make the leap. Newton and Gallileo worked by themselves and without significant competition.
I also think that Einstein's work, while we see little of it in daily life, will have the greatest impact on the future.
So chalk one up for old Al.
I've read that while special relativity was "in the air," so that someone else would have come up with it, general relativity was so theoretical, and so austere, that it might have taken another century for others to piece together all the clues (which came later) and produce that theory. But I'll leave this to those who know more than I do.
It seems to me there are at least two crowns in contention here: who made the most inherently impressive technical contribution, and who had the the greatest social impact. For the former, I'd have a tough time putting either Maxwell or Gauss behind the current contenders, and for the later, I'd nominate Plato, for inventing the idea that governments should pay certain people to sit around thinking all day, and Roger Bacon, for pushing the idea into a modern context, and selling the snot out of it.
"But I have come to the conclusion that when the time is ripe, the discoveries will be made."
And how do you know the "time was right"? --Because the discoveries were made.
Kind of tautological. (Like survival of the fittest. LOL)
Pressures were just as intense in Newton's day, and more personal. It was cutthroat competition, literally.