I would venture to guess that just about anyone reading this blog is familiar with Ken Wilber. It certainly seems to me that he belongs on the list. However, there's a theoretical physicist who didn't make it who surely belongs there as well.
Of course, Stephen Hawking is on it, possibly mostly because he's British, is an extremely well-publicized victim of ALS, has written a very popular book about cosmology, and has made some important contributions to astrophysical theory. It's also true that Hawking occupies Isaac Newton's chair as Lucasian Professor of Mathematics at the University of Cambridge and is popularly thought to be Newton's and Einstein's successor.
Yet, the person regarded by his fellow physicists and mathematicians to truly be the most likely successor to Einstein is an unassuming scientist at Einstein's old stomping grounds, Princeton's Institute for Advanced Study. His name is Edward Witten. He clearly possesses what the late, great physicist Richard Feynman called a "monster mind." Or as one prominent cosmologist said of Witten: "We all think we're very smart, but he's so much smarter than the rest of us."
Witten has won a MacArthur Grant, the National Medal of Science, and has the highest h-index of any living physicist. This is a measure that attempts to quantify scientific productivity and impact. He's renowned for his grasp of and contributions to both mathematics and physics and is a winner of the extremely prestigious Fields Medal, the mathematics equivalent of the Nobel Prize. The great geometer Sir Michael Atiyah said this of Witten:
Although he is definitely a physicist (as his list of publications clearly shows) his command of mathematics is rivalled by few mathematicians, and his ability to interpret physical ideas in mathematical form is quite unique. Time and again he has surprised the mathematical community by his brilliant application of physical insight leading to new and deep mathematical theorems.
Witten is probably most famous for his spectacular contributions to superstring theory, and the video below features theoretical physicist Brian Greene touching upon Witten's involvement in this area and also shows Witten briefly.