Mark Peters has a wonderful column at McSweeney's Internet Tendency on the "Best Joke Ever." Today's is on Mitch Hedberg, and it crystallizes one of his unique points, over and above his creativity. Hedberg's delivery and countenance - his eye-contact avoiding shades and hair, how his body almost folded into itself - allowed for "joke" telling, as opposed to a routine. He made the audience forgive his embrace of the joke, a seeming holdover from another time, as there was almost a sense that he might leave the stage at any time. He spoke in a drone, but it was an A chord that resolved back to the E.
Peters might be right that the broken escalator is his best joke, as much as it wholly integral and can be removed from his performance context to be retold by virtually anyone, but I don't know if it's the best thing he ever said. I'm partial to his ethnographic description of the stand-up performance (it's prefaces my chapter on the stage in A Vulgar Art):
Watch it here: he closes with it but the entire routine is worth watching. And it's only five minutes: like you're such hot shit you can't spare five minutes?