… is …
To those who do not know him (shame on you; shame on me coz as of lately I did not know him either), it’s Fred Astaire. Now why do I say that according to imdb he is the best all-time actor? The answer is very simple – look closely at the provided link – especially at its last part: nm0000001. He was the first actor to be added to the imdb database when it was being created. This cannot be just pure coincidence!
PS: Unfortunately, the first added movie (with 0000001 index) is some 1894′ 1 minute short called Carmencita (1894) and it’s not widely known.