SB good post. Most viewers tend to dismiss Sonny as a hothead but in reality Michael also had tragic faults as large as Sonny and Fredo.

Vito was an extraordinary Don because he would both inspire great fear/respect and LOVE among others. He had a way of binding others to him that were thought untamable like Luca Brasi and yet his lightest touch had a profound impact on those who barely knew him like the baker who refused to leave Michael's side at the hospital.

Michael's tragic fault and the tragedy of the trilogy is his inability to balance these aspects. While Vito was benevolent even when he had men killed, Michael's actions serve to alienate him farther and farther from not only those he loves but himself as well.

Sonny had an aspect from Vito that commanded respect. To the end, Michael was never able to command the respect or love his father had and that was his undoing. If Sonny had remained alive the other families and the Corelone's allies would not have underestimated him as they did Michael. I believe that eventually he would have been in a position to bargain with the other families as Vito did for Michael's return and also that Tessio would not have turned traitor. I believe that Tessio's primary motivation is not greed but his lack of faith in Michael's "weak" leadership and the Family's weak position after the Don's death. While Sonny might have been overly violent, you can see from all 3 movies that the conflict in these movies were all put into play when both the Corelone's lieutenants and their enemies misread Michael's complicated long-term internal machinations as weakness,

It's hard to say what would have happened if Sonny had lived. Certainly Michael, having been linked to the murders and fled would never have been able to go completely legit or have been elected Senator as Vito hoped but he probably would not have been personally responsible for so many deaths that eventually drove Kate and his kids from him.

Ultimately, Sonny would not have been as good a Don as Michael, since he didn't have Michael's cunning and long-term vision. In intellect and material successes Michael surpassed the old Don, which Sonny would have been very hard pressed to come close to. For Michael personally, he wouldn't have ended up alone such a tragic figure