Elvis, Chris Cornell, and even John Lennon were probably well past their peaks (age 40+) and not likely to come up with music as good as they did when they were younger.
As much as I like SRV, I don't think he would have ever gotten much more traction than he had since he played relatively niche music.
I think Hendrix is the answer. Still young and in his prime, and died right at a time when 70s hard rock was starting up. I would have liked to see how he responded with the times.
No one actually sits around listening to Mozart, so that pretentiousness can go ahead and stop. Liking "everything from classical to hip-hop" doesn't make you special, it makes you unable to make up your mind.