RESURECTION
Okay guys, I have recently watched all of the Avatar series and the Sword Art Online series. WOW, just wow. Thanks to this thread for making me check out Avatar and thanks to Avatar and the Oculus Rift for making me watch SAO.
Avatar was really great. I can think of very few series that I would happily watch all the way through again, would enjoy myself nearly 100% of the time, and also managed to wrap up the story so satisfyingly. It was just perfect. I've already seen many of the episodes two and three times because I've watched some of them again with my son. I still have a desire to someday run through the whole series in order again. Just the right tone. (*)
To me it stands above other great series like Full Metal Alchemist (which I might be willing to slog through one more time) and Inuyasha (more episodic and then just drags on and on trying to best itself into an ultimately fairly unsatisfying conclusion, later movies aside).
* - an episode that I really think shows the depth of thinking involved in Avatar is the one that is dedicated to Mako who did the voice of Uncle Iroh. "Tales of Ba Sing Se" manages to mix the adventure and quirky humor of the show together with the deeper tale of Iroh putting together a picnic for some special occasion. Along the way he helps a lot of people, including a little boy to whom he sings a cheerful song about a boy coming home from war. It is finally revealed that the picnic is to remember his dead son's birthday. His son had died in the previous war and Iroh wishes he could have helped him like he helped all of the other people. He sings the same song again only now it takes on a different meaning in context. By the time the dedication to Mako pops up, I was nearly completely unraveled.
...but I think it shows the level of thinking and subtlety that went into the stories and characters. How even taken in total, the motivations and transformations are clear and consistent, and often lightly foreshadowed all the way from the first episodes. Just really excellent story-crafting.