Obviously, he's intended to be, and at least in the book and first movie, it's easy to sustain. If timing of the gang war is just a little different, he has a good chance of an uneventful life. In the latter films, it becomes more difficult to sustain the notion that Michael is being carried along by events. He's too active a participant over too long a period of time to maintain the appearance of a victim of circumstance.

Another thing to consider is that there's really no indication that Michael thinks what the Family does is wrong. It's old-fashioned and inefficient, but at bottom no more corrupt than other organizations.