PASSING STRANGE was the first to came to my mind, honestly. That show stands alone in so many ways, I still think about it.
I think, as an exercise in construction and execution, JERSEY BOYS' libretto deserves to live on as an exemplar of the good jukebox libretto. But I wouldn't call it legendary.
Words don't deserve that kind of malarkey. They're innocent, neutral, precise, standing for this, describing that, meaning the other, so if you look after them you can build bridges across incomprehension and chaos. But when they get their corners knocked off, they're no good anymore…I don't think writers are sacred, but words are. They deserve respect. If you get the right ones in the right order, you can nudge the world a little.