Answer:
Galileo, Newton, and Einstein deserve this special recognition because they not only built on and made advances in the knowledge of those who came before them, but they also each had significant new concepts of their own. A physicist that im very fond of, but is sadly overlooked is Stanley Mandelstam. This man, in my opinion, is certainly one of the greatest living physists alive, although he is very old. In 1957, he discovered the double-dispersion relations, and essentially refounded S-matrix theory, which was proposed by Heisenberg in 1941, but lay dormant for nearly 20 years. This theory became string theory, after many twists and turns, and Mandelstam is the original formulator of 2-d conformal fields, fermionic correlation functions, string field theory, and the arguments for finiteness of string perturbation theory which convinced the world that the theory had no ultraviolet divergences. He also made pioneering contributions to field theory, and really, he deserves a major overdue Nobel Prize, but he'll never get it. However, he was truly too advanced for his time, and wasn't understood.