I suck at history so I had to look up what Mount Rushmore was built for. So based on a reliable source, Wikipedia, the four presidents in Mount Rushmore were chosen to represent the nation's birth, growth, development and preservation, respectively.
If I were to follow the same reasoning for selection, I'd have to say Preston Parker (started for me in BangBros), Cody Cummings, Carter Woods, and Tim Kruger, respectively.
If I were just to pick my all time porn favorites to date, then I'd say, in no particular order: Carter Woods, Dante Colle, Griffin Barrows, Max Adonis; although I would prefer to have more than just their faces in the mountain ????