This line from the film On the Waterfront generally appears on most lists of the greatest or most famous movie lines ever uttered:
You don't understand. I coulda had class. I coulda been a contender. I coulda been somebody, instead of a bum, which is what I am, let's face it.
I've never understood this one. From my perspective, it is not especially climactic or elegant; there's no clever wordplay or incredibly original joke; the wording is not particularly memorable or unusual; the scene is not extraordinary and so the line cannot take its fame from the scene; the content of the line is not especially revelatory or disturbing or surprising.
In short, it has none of the attributes of most other famous lines.
Why is this line so famous?