I was going to add Ronnie Van Zant/Steve Gaines. Seemed like they were going to have at least another good album or two in them.
I voted Jimi because he was super ahead of his time and seemed like he was heading in the direction of doing more and more interesting shit.
I'd be really curious about what Cobain would have done. I honestly have no clue.
the truth is most if not all had probably peaked though.
Almost all probably have controversial political opinions if they're still alive.
This really is easy. Hendrix was just getting started. He was going through a bit of a reset and never should have moved away from the original Experience power trio. Mitch Mitchell was nearly as much of a force in that setup as Hendrix was.
However...look at the way the harder end of the rock spectrum was evolving in 1970 and where it went. Does anyone really think Hendrix would've stood by and watched bands like Sabbath, Led, and Deep Purple leave him behind as a hard rocker? I believe that would've been his direction and it would've been glorious.
Morrison was talented but he was a fuck stuck and a clown. I used to have a disk of Hendrix jamming in some club. Pretty shitty jamming but that's jamming for you. Morrison got up there with him, noticeably, incoherently drunk, and made such a fool of himself that I had a hard time hearing even his Doors stuff for a while after. Man he sucked. You could tell Hendrix was embarrassed.