In terms of deep contributions to a variety of mathematical science type fields, probably no one. People might say Terence Tao, and of course no offense to him he is extraordinary smart and widely knowledged, but in my opinion he hasn't made the same level of deep contributions to mathematics let alone other fields. From what I've heard and read historically to be considered one of the "greats" so to speak you had to have full mastery of a field, either by starting it or revolutionizing it (funnily enough von Neumann was criticized for this by other mathematicians in his time). An easy example is Alexander Grothendieck, who is considered one of the top mathematicians of the 20th century. He revolutionized algebraic geometry and homological algebra. For von Neumann the most obvious field would be operator algebras. Of course the reason for mathematicians these days not being as "creative" or "revolutionary" may just be that all the low hanging fruit so to speak has already been picked, which in my view is the most obvious reason, so it's significantly harder to make deep contributions compared to times past, but it is what it is.