Was he a great actor? Was he even a good actor?
He did have that "great actor" reputation through the sixties, or at least part of the sixties, then his career took a swan dive and he became known as a scenery-chewing ham who'd do anything for a paycheck.
He did give some very good performances, in films such as "Who's Afraid of Virginia Woolf" and "Becket", and some very bad ones in crap like, well, everything he did with Liz Taylor. Are a few terrific performances enough to rescue his reputation?