I thought Michael wanted his son into the business. I really dont like the ending but it sounds good. The door geting shut in his face wouldn't be godfatherish because the hole trilogy is about him and it would be stupid in the last movie to have him look stupid and weak.

If you had any fucking heart at all you'd be out stealin'! Joe Pecsi
Turn that thing off! You should be out stealing! Lefty
You put up and shut up, you hear nothing you say nothing! Just like you did for Bugsy! -Noodles