True. But Newton and Einstein revolutionized our understanding of the universe in a way that a Feynman, Hawking or Gell-Mann didn't. I doubt these gentlemen would have disagreed with that.
Newton will sort of always stand apart in that he was "the first", but I think that grouping Gell-Mann (no pun intended) with Hawking and Feynman, who although both brilliant and huge personalities, weren't the same level of "giant upon whose shoulders others stand" that Einstein and Gell-Mann's work ended up being is somewhat unfair.