Although I sometimes fail to agree with Time when it dubs something a masterpiece (When I think that Wilder went on from this to 'Some Like It Hot', for instance...) there is no denying that 'Sunset Boulevard' remains immortal.
The stylish noir imagery and flamboyant yet convincing acting are only part of the secret.
To me, Wilder's storyline is absolute genius, for all its misogyny. Multi-layered only begins to describe it : You may view it as a reverse 'Pretty Woman', highlighted by the inherent ridicule of a middle-aged woman still eager to please. You can also read it as a not-so-subtle statement on how the Hollywood dream factory consumes not only people but also their dreams. (Hollywood on Hollywood : So mise en abyme it hurts!) Moreover, it is a comment on mental disorder. And on love. And probably a lot more that I didn't perceive.
A masterpiece, I tell you.