Pygmalion

Nearly 70 years later the Gabriel Pascal "Pygmalion" still sets the bar for film adaptation of a stage play. So much so, in fact, that the GBS incorporated many of the film's upgrades into the authoritative published version of the play, despite the play being more than 20 years old when the film was made.

When was the last time you saw a performance leap off the screen like Leslie Howard's as Professor Higgins? Shaw never saw such treatment on screen again, even under Pascal's hand. The film of "Major Barbara" is interesting (and a bit bizarre toward the end) in its own right, with some magnificent bits in the Act II homeless shelter and a heart-wrenching Wendy Hiller, but pales next to the stage version in its intellectual, political and dramatic depth. And all the rest, even the charming "Caesar and Cleopatra" with Raines and Leigh, just don't cut it compared to the plays.

"Pygmalion" is where any screenwriter needs to start in adapting a play for the movies. No one has done it better since.

(BTW, GBS's afterward to "Pygmalion" is intended to be tongue-in-cheek, I think. It's intentionally ridiculous, so that the mob clamoring for a romantic ending would realize just how inappropriate and uninteresting that would have been.)