He was an odd actor. His performances ranged, I think, from superbly compelling to horrendously self-indulgent (in some of the later films). I sometimes got the feeling that he ardently detested himself and everybody else. That doesn't seem like a very good premise on which to base a life or an acting career to me, but he certainly did have panache whenever he appeared onscreen. His early films were unforgettable. His later ones ran the gamut from very good to just plain bloody awful.
Joan Baez revealed in her autobiography that she had been utterly transfixed by the young Brando, and she wondered why he "decided to get old so soon"? I wonder about that too. Well, she finally got to kiss the "old lion" on the cheek at some point...decades after "The Wild One". :-)