Evidently, He didn't want that life, that why he joined the military. Circumstances made it a nessacity, we already know that. IMO it doesn't matter if he wanted to, He needed to protect his blood family from harm, that was his duty. Protecting his Fathers business came with that responsibility. All the actions at the end GF1 proves this. In GF2, Now its his business and the legacy of his family both the mob and blood, that he must protect. By that point, It was his life, it was apart of survival. Michael was able to supercede Don Vito because he learn from his experience in the military and going to Sicily, gave him the training of a true Mafioso (in the context of the story).