I thought the ending of the Wire was apropos. The old generation died/was sent to prison, the new generation came up to take their place. It reinforced the theme that the ghetto was a trap, even when these kingpins tried to go legitimate once they had the capital to do so, they came up in violence and only knew violence and, in some ways, needed violence.
And McNulty settled down. Which was a bit boring, he probably should have been shot.