Avatar The Last Airbender shouldn't be underestimated. For a while I didn't even look twice at it due to it being on Nickelodeon and me being past the age of watching anything on Nick aside from the classic Nicktoons or Nick shows from the 1990s. But word got around that it was really fantastic, a sort of Kung fu style show where a master goes from place to place having adventures. Turns out the people I heard the word from weren't kidding: the saga of Aang, the last airbender and Avatar, who masters the four elements (air, earth, water, fire) and has to save the world by stopping the power-hungry fire lord, Ozai, is as epic as anything I've ever seen. It's an achievement of storytelling that creeps up on you, and while the first season isn't perfect the second season delivers episode after episode that enriches the characters and makes us care about them as we would in, for obvious example, Star Wars.
In fact, the only minor complaint I would have against the second season (not sure yet about the third) is that it borrows quite heavily from the Empire Stikes Back (i.e. the 'one-who-will-save-us-all' mythology from Joseph Campbell is off training with an old master, feels his friend(s) in pain and danger in the future, rushes off before finishing training, bad things ensue, etc). But really, all of the characters get developed quite well, and if anything the development of the character Prince Zuko, a scarred son of Ozai who has been banished until he can bring back the Avatar along with his banished uncle Iroh, is astonishing in its complexity. We don't care about this character at first, in the first season he comes off like a whiner with Iroh as the wonderful comic relief (think Pokemon if the brother and sister weren't so annoying). But by season two a whole other dimension comes into play: who are you, and what are you doing with yourself?
The trek with the three main characters, and the extra characters like Toph (a little blind girl who is one of those great bad-asses you have to see to believe), is one that is sophisticated enough to bring in adults, and for kids it's often just rollicking fun when it isn't deep or dark. The villains are convincing and scary, the humor hits when it needs to (and sometimes it can be just downright trippy and hilarious, like the second episode of season two, the Cave of Two Lovers), and the animation is often breathtaking. As they say on the internet now: it's made of Win!
