Other Disqualifications:
Tupac and Biggie- Their music became more popular AFTER their death and possibly because of it. Besides, I am convinced they are alive and well somewhere in Cabo suckin' down margaritas.
Dimebag Darell-famous for being shot on stage. However his music wasn't really influential and he is more famous for how he died.
Keith Moon- Roger Daltry and Pete Townshend were really the creative heart of The Who.
Honorable mentions:
Brian Epstein- Not a musician, but he was the manager of the Beatles until his death in '66. That was when the Beatles' egos flared and they started fighting. We might have had more Beatles without his death.
Duane Allman- named #2 guitarist of all time by Rolling Stone, would he be better than Clapton if he lived? They at least would have made more music together than Layla
Aaliyah-Just on the verge of superstardom. By all accounts very hardworking and down to earth.
5. Robert Johnson- the only member of the "Forever 27" club on my list. If you don't know him, the song "Crossroads" is by him as well as about him. His guitar skills came about so fast people thought he sold his soul to the devil for his talent. His genius is also that he never denied it. He died young after only a couple of albums and under mysterious circumstances. Blues artists of the same era made 3 times as many albums and are largely unremembered. The little but of music Johnson made influences rock legends of today.
4. Marvin Gaye- He had just on a Grammy for his song "Sexual Healing" before his clergyman father murdered him. Very sad.
3. Selena- not really my type of music, but she was just becoming a star when she died. She had a lot more music in her, and unfortunately her death has sold more J. Lo albums than her 3.
2. Bradley Nowell- Sublime had just signed with a major record company. He had an amazing voice and songwriting talent. I so wish we could've had a couple more albums from him and his band.
1. Buddy Holly-He went down early in his career and the Beatles themselves attribute all their success to his influence. The "Beatles" name itself is in honor of the "crickets" who backed up Buddy Holly. Where would his career have gone if he stuck around?