Most disciplined Historians would say that the greatest anything varies according to the time the observer is living through.

So I also go with the few people who said that there really is no "greatest" scientist or philosopher.

By the way, an Historical fact, which CAN be illuminating, if you think about it enough: the distinction we NOW make between Philosophy and Science was once not there. Especially in that whereas now, lots of (especially the more uneducated)people think that "philosophy" means "just made stuff up out of thin air and wishful thinking." Science was once called "Natural Philosophy" specifically because the same thinking and observation required for good science, is also required for good philosophy.

Which is why I have a PhD, or Doctor of Philosophy, in Molecular Genetics (Natural Sciences)

It's hard to pick any individual as so many have given so much to humanity.

On a side note about science and philosophy, what could be greater than a mother giving birth to her children or a soldier giving his life for our freedom, all these people are as great as the most famous scientists even if most of them are unknown.

Hero of Alexandria could be a major competitor...
https://en.wikipedia.org/wiki/Hero_of_Alexandria
Hero described[6] the construction of the aeolipile (a version of which is known as Hero's engine) which was a rocket-like reaction engine and the first-recorded steam engine (although Vitruvius mentioned the aeolipile in De Architectura some 100 years earlier than Hero). It was created almost two millennia before the industrial revolution. Another engine used air from a closed chamber heated by an altar fire to displace water from a sealed vessel; the water was collected and its weight, pulling on a rope, opened temple doors.[7] Some historians have conflated the two inventions to assert that the aeolipile was capable of useful work.[8]
Hero's wind-powered organ (reconstruction)

The first vending machine was also one of his constructions, when a coin was introduced via a slot on the top of the machine, a set amount of holy water was dispensed. This was included in his list of inventions in his book, "Mechanics and Optics". When the coin was deposited, it fell upon a pan attached to a lever. The lever opened up a valve which let some water flow out. The pan continued to tilt with the weight of the coin until it fell off, at which point a counter-weight would snap the lever back up and turn off the valve.[9]

A windwheel operating an organ, marking the first instance of wind powering a machine in history.[3][4]
Hero also invented many mechanisms for the Greek theater, including an entirely mechanical play almost ten minutes in length, powered by a binary-like system of ropes, knots, and simple machines operated by a rotating cylindrical cogwheel. The sound of thunder was produced by the mechanically-timed dropping of metal balls onto a hidden drum.
The force pump was widely used in the Roman world, and one application was in a fire-engine.
A syringe-like device was described by Heron to control the delivery of air or liquids.[10]
In optics, Hero formulated the Principle of the Shortest Path of Light: If a ray of light propagates from point A to point B within the same medium, the path-length followed is the shortest possible. It was nearly 1000 years later that Alhacen expanded the principle to both reflection and refraction, and the principle was later stated in this form by Pierre de Fermat in 1662; the most modern form is that the path is at an extremum.
A standalone fountain that operates under self-contained hydrostatic energy. (Heron's fountain)
A programmable cart that was powered by a falling weight. The "program" consisted of strings wrapped around the drive axle

All and none.
Each contributed.
What constitutes greatness may be a further question?