P. Gabriel,
Your like of my post #3,595 reminded me that the same "what if" question I had with Syd Barrett I also had with your namesake, Peter Gabriel, and Bon Scott. Although I do not pretend to be a knowledgeable music historian I do like playing the "what if" questions like these:
1. What if Peter Gabriel had never left Genesis?
Answer: I think the short answer to this question is that things would not have turned out as well as they did for Genesis, for Phil Collins, and for Peter Gabriel himself.
2. What if Bon Scott had not died? Would AC/DC have been as successful?
Answer: They would have been even MORE successful.
3. What if Syd Barrett had not fucked up his head using drugs and stayed with the band Pink Floyd and remained in the music industry?
Answer: this is the hardest question of all to answer. Barrett was a musical genius and the frontman and leader of a band filled with brimming talents in Waters, Wright and Mason. It seems likely David Gilmour would not have joined the band had Barrett remained in the band. Would Pink Floyd have had the same level of international success? It's hard to say but I am going to give it a maybe.
4. What if John Lennon was not shot and the Beatles did a reunion tour and album as was widely rumored to happen in the year before Lennon was killed?
Answer: The tour would have made immense money to pad their immense respective wealth, but any new music would not have been as good as what they did in the 1960s.
5. If Jimi Hendrix, Janis Joplin and Jim Morrison had all lived, who would have produced the most memorable music from the point of their death forward?
Answer: I think that Jimi Hendrix was the least fated to die of these 3, and the most "responsible" drug abuser of the 3, his death being caused by involuntary restraint causing asphyxiation on his own vomit and not so much his own behaviors. I suspect Jimi would have had a long career of productivity because he could take music of others and do something entirely different with it as well as write his own stuff, something proven by what he did with Dylan's "All Along The Watchtower." Morrison and Joplin, sadly, were trainwreck addicts who were eventually going to crash.