Brando's style was so intimate and authentic that it has essentially become the measure against which contemporary film acting is evaluated. For my money he's the greatest.

By far "the Godfather"

In The Godfather he had an excellent voice for the part he played.I think this is his best movie.

Streetcar Named Desire.

Excellent choices Irish, and followed by the Godfather.

On the Waterfront. Streetcar Named Desire is a close second

Burn

The decline in quality in some of Brando's later projects probably resulted from his personal detachment and disregard towards his craft as a profession of social significance. And yet, he, along with John Garfield, Montgomery Clift and James Dean, defined the art of acting for many of those who followed: the Paul Newmans, Dustin Hoffmans, Al Pacinos, Robert DeNiros, Kevin Spaceys, Johnny Depps, etc. Brando is there all over Ratso Rizzo, Travis Bickle or Michael Corleone and would have made Jake LaMotta equally sensational; Scorcese would know.

Best movie. Hmmm. A Streetcar Named Desire; On the Waterfront; Viva Zapata; Apocalypse Now; The Godfather. Can't make up my mind. His best performance? The list would grow larger.