The character of Andy Sipowicz, played by 4 time Emmy winner Dennis Franz, was the most realistic character ever created on television, faults and all. He was a modern-day everyman, and that was why we rooted for him, even when he was in one of those moods. It was why we continued to watch right up until it's triumphant end.
It came along when the one-hour drama on network television was all but dead; it re-defined the look of prime time drama with language and wardrobe (or lack their of), as well as how it was filmed; and when you speak with anyone that is or ever has served in law enforcement in this country, they'll tell you it was the best show at capturing "The Job" from a realism and accuracy standpoint.
Thank God for re-runs.