I appreciate them both in their own right.

Part II the regret was implied. You could realistically think that Mike thought he was justified in killing Fredo and everyone else without regret.

But the ending of Part III showed you that Mike was full of regret. It beat you over the head with it.

And I think the ending of Part III was fine. It was short and sweet. To drag it out any longer, to show Mike at a funeral, anything.... would have made the film longer than it needed to be.

I am with DMC. The silent scream to the credits of Part III is probably my favorite 90 secs or so of cinema. Simply amazing.