I am a HUGE fan of Black Sabbath, but truth be told he was totally the weakest link.
Never wrote anything and was never a great singer--even when he was in full voice.
He DEFINITELY got lucky on four counts:
1. he met/married Sharon--who, while a total bitch did wonders for his career. He was probably destined to homelessness if he didn't meet her.
2. Getting Randi Rhodes. This guy was a total game changer. Only Eddie van Halen was more influential to '80s guitar. He set the scene pretty much for what was expected for any metal band for the next 10-12 years.
3. The fact that no one really caught on to the fact that his (and Sharon's) dealings with songwriters and musicians was about as scuzzy as anything in the industry.
4. He didn't die in the 70s or 80s.