Not sure there's ever been an equal in the realm of how badly drugs can destroy genius without it killing them.
He was Prince before Prince was Prince. The band was his instrument. He was Zappa with a funkier and hookier focus. Sadly, he was also a debilitating addict. It a shame that he never really pulled out of it to come back on his terms, with his band, doing his music (ideally new music), and not as a side show.
Despite the greatness he created/achieved, he still had so much potential before he decided that being high was his favorite thing. The doc makes it seems like creating and playing music used to give him that high, but then it became easier to just do a shit ton of drugs...
It's like he was a member of the 27 club, but it's just his musical creativity that died...or at least his prioritizing of his music that he let die.