I agree, that comedians are amazing at crafting the delivery of a joke, where one word out of place could ruin it. The selection of the right word, the timing, the delivery all are what makes the joke hit or miss.

but there are different ways to sing a song, to approach it, deliver it, emphasize different words. A sinatra rendition could be quite different from a Mel Torme rendition

I realize the character comedians like Pee WEE, or the wild and crazy guy version of steve martin could not be duplicated.

the reason I asked is that expectations change over time. In the late 70;s I saw the Who, and they were killed in the media for having a 30 second canned synthesizer intro to Baba Oreily(they dont have a syntesizer player in the band)......in every review of the madison square garden show they were hammered. Now there are acts that have canned vocals and music for entire songs while the artist dances and lip sinks. Totally accepted.

It is a shame that all that material gets buried with the comedian. Great songs becom standards and get passed down through generation with new blood singing them. Painters great works are memorialized in museums for generations to see.
Not so with comedy.....it dies...its disposable.