When it comes to film acting, I'd say the greats are rarely the biggest stars, just like the best films are rarely the biggest box office grossing films.

Sometimes you can see an actor's greatness early on, as was the case with Meryl Streep, IMO.

With others, as I would suggest is the case with James Earl Jones, the promise of greatness early on, is never realized.

Then there are those who become great through a body of work over an extended period of time, including outstanding performances in mediocre and sometimes even bad films.

It is nigh on impossible to rank people on this basis anyway. Even the most talented, gifted actors make bad choices and turn in poor performances, overact here and there, that sort of thing. Some of these people become better known as stars than for their acting ability, which I think is the case with Brad Pitt.

Then there are some of the best actors who have quietly turned in remarkable performances over and over, who are virtually ignored by the industry, like Alfre Woodard, whom I mentioned above. I can't think of a single thing I've seen her in where she didn't shine, or even carry the film.