I agree with this assessment, Turnbull. I had never really thought about this point, but Michael did have the possibility, albeit a small one, to return to his previous life after the Sollozzo murder. Had Sonny & Appolonia not been murdered, Michael's sense of "duty to family" would not have been as strong. As he stated throughout the Triology, Michael was ALWAYS looking to protect his family. Once he saw that his family was vulnerable after his wife & brother's death, Michael felt that protecting his family was his #1 priority. The sacrifice was entering the business he grew up despising, which I believe Michael felt was a necessary trade-off for protecting his family. The great tragedy is that Michael failed to protect those he loved most in his family: Sonny, Appolonia, and Mary. Kay was almost killed from the traitorous act begun by Fredo. In reality, the ones that survived with Michael were Mama & Connie.