Years ago when I heard Nickelodeon was making an anime inspired Nicktoon, I wasn't that interested at the time. On first impressions alone I originally had low expectations about it since it was a Nicktoon and it wasn't going to be taken that seriously. I was sorely mistaken and, looking back, I admit that I missed out on it back then. Osuka, who is one of my closest friends, has been recommending the animation ever since I met him years ago. Then When Doug Walker started his Avatar Vlogs, I was curious to see what all the fuss was about.
I was not disappointed, it's a great series. Fun likeable characters, interesting plot, occasionally legit funny moments and beautiful artwork. From the very beginning the show took itself very seriously but at the same time not losing that optimistic sense of adventure. it even has an accurate explanation of the concept of Chakra (In comparison to Naruto where Chakra is compared to Magic in RPGs or "the force" in Star wars). Watching the entire Last Airbender series during the summer I can assure you it is a highly recommended show for all ages. The first season was a little rocky at times, but the show improves in the 2nd and 3rd seasons.
Originally I chose to watch the first three seasons in order to get an Idea as to why Shyamalan's "The Last Airbender" was so bad. And it is! The story is too rushed (season 1 squished into a 90 minute film), the actors are awful, extremely odd casting, way too many plot holes and the visual effects, though OK at times, just comes off as poor. in short, M Night Shyamalan should stay away from Avatar. There are rumors of a sequel, but it shouldn't be made at all.
Now when it comes to the spin off series The Legend of Korra, it was a bit hard to get used to considering the drastic changes that were made in comparison to the original(TLoK taking place about 70 years after the original series), but overall the new series grows on you over time. The best way to describe both shows would be to compare the first Avatar series to The Never Ending Story in terms of fantasy adventure and the Korra spinoff to 90s Batman cartoon being dark, serious and somewhat adult with the political turmoil and terrorism.
Now the first season of Korra was a bit rushed considering that it was originally given a 12 episode run, but none the less it was an enjoyable run. Thanks to this, there will be 3 more seasons out and I'm looking forward to them. I'm currently watching season 2 right now and, just like the first series, it has started to gain momentum halfway through.
In closing, if you're new to the Avatar universe, I say check it out. You have to let it grow on you before you start to appreciate it. You will not be disappointed.