Greatest ever Actor

?
You did not specify that you are limiting this to big money movie stars. That lets out thousands of theatre actors and low-budget indie movie actors.
But even if I accepted your "pop culture" limitation, anyone who ever saw "Death in Venice" would have to at least mention Dirk Bogarde, er, SIR Dirk Bogarde. Not to mention Rain Man (Dustin Hoffman).
And so Anglo-centric? Where is Toshiro Mifune? Gerard Depardieu? Amitabh Bachchan? Shah Rukh Khan? Max Von Sydow? Bruno Ganz?
You can tell I have wasted years of my short (and getting shorter) life watching movies.