I think what I really love about them comes down to 2 things. One, they don't pull any punches, but it's rarely just gratuitous gore, it all follows from what's happening. Two, each one ends with a knowledge that the work goes on, and yes, there could be a sequel, but there's not a necessity of a sequel. Any one of them could end the series with satisfaction, but each one lets you know that the game's not over. No happy-scrappy-everyone-goes-home-happy endings, here. There'll always be people out there in need of a lesson, and John's work will continue, even after his death.
Couple weeks, I just might do them all again. Watching them with the foreknowledge of what's going on behind the story isn';t hurting it for me, it's making it that much more interesting to watch the development.