Interesting point, Olivant- was Vito really that much against the purveyance of narcotics? Was he able to see past Tom's warning that without narcotics they risked everything they had, "not now but ten years from now"? was he really able to see that the narcotics racket truly would "destroy us in the years to come"? (As it indeed eventually did- LCN is a shell of it's former self)...
Big Picture speculation here- Sonny would have lived, Vito would have lived longer, securing more time and training in the more subtle qualities of being a Don for Santino- who would have gone on to become the Don upon Vito's retirement. Fredo would have remained the low-level gopher, but for his older brother, as opposed to his kid brother- Fredo would perhaps not made the same mistakes that he later did.
But Vito's greatest triumph would have been that he finally would have had "enough time"- Michael would have stayed out of the Family buisness, the Family would have moved towards more legitimate enterprises with Michael at the lead of that side of things- perhaps not Michael, but Anthony, or even Mike and Kay's aborted son, may have gone on to become "Senator Corleone, Governor Corleone, something..."

Sammy The Fish