The question is too vague to have a tangible meaning and because of that is prone to unscientific personal subjectivity.
The irony is, the question is "who is the all time best scientist ?.
The scientific process is too gradual to settle this question conclusively, Newton himself, paraphrasing Bernard of Chartres, is credited with alluding that if he can see further than the giants of old, it is because he was standing on their shoulders (Hawkins has a book "On The Shoulder of Giants" chronicling the works of Copernicus, Galileo, Kepler, Newton and Einstein). But even if I was to narrow this down to these giants, who is to say that Hawkins is not biased by Physics in his choices, and neglected Mendelev, Pavlov, Darwin and Hooke?
What if I go back and say Erasthothenes by discovering the circumference of the earth in 240 BC ?
What about Imhotep and Socrates and his Socratic method without which science wouldn't exist?
You can have the greatest biologist, physicist, chemist etc because you are dealing with a single discipline.
Science, as illusory as the oversimplification of that designation may prove, is a single method but not a single discipline.
Even within a single discipline as physics, comparing Niels Bohr and Albert Einstein is easy because they were contemporaries in physics. Comparing either to Newton is disastrous, as both used Newtons equation to derive their own equations.
The case becomes even more complicated when you start to compare Einstein and Darwin. Two great scientists from two totally different disciplines of sciences and two totally different eras.
You not only get the proverbial comparison of apples to oranges, but also earthly 3d apples to Kaluza-Klein's spacetime continuum's equivalent of oranges.