I would rank Buster Keaton in his prime at the top. Chaplin a close second up to maybe The Great Dictator. Hard to pick a third after those two giants whose work is fast closing in on the century mark. That means their work is no longer due to popular taste at the time of creation but morphing into timeless art. Now that I have thought about it Lucille Ball during the I Love Lucy run. So Keaton Chaplin Ball.
Well what about the guy who was just as big or bigger during the silent era, that would be Harold Lloyd!!!!!!!