OK, so I was 12 when this show came out and needless to say, I was completely enamored by it. For a TV station like Nickelodeon, best known for its wacky shows like SpongeBob, Rocko's Modern Life and their sitcoms like Drake and Josh, to suddenly come out with this anime-inspired animated series with deep philosophical themes as well as tackling genocide and war, this was a massive step forward.
Of course, this isn't the first form of media that has incorporated the power of the elements, but their method of how they do it here is remarkable. For every element to be adopted into its own nation, reflecting the psyches and philosophies attributed to the respective element is truly inspiring.
All the characters are written for and performed expertly, save for maybe some of the guest characters (*cough cough* Jet). My favourite character by far is Zuko. The progression and development of this character is incredible and captures perfectly the transition from villain to antihero to hero. Aang is a good character too, but he's a bit of a goody-two-shoes half the time. Katara and Sokka are equally appealing characters, as well as Toph.
The brilliance of this show is that it is perfectly paced. Sure, you get the occasional filler episode, but every episode (leaving out The Great Divide) has a purpose and adds more layers to this intriguing story and the world it is set in.
Again, for a children's show to incorporate seriously heavy topics and still have a silly sense of humour is just impressive. I get annoyed every time someone stereotypes this series as just a 'kids show', brushing it off. This show can be watched by someone of any age, and that is one of the reasons I admire it so much. It's not pandering at all and tackles the heavy subject matter in a mature way.
Sadly, after The Legend of Korra, Nickelodeon never seemed to follow in the footsteps of Avatar which I found upsetting. Kids need more shows like this, if I'm being honest.