The series is heavily influenced by various Asian cultures, the word 'avatar' being used in the sense that it is in Sanskrit, to be a reborn descendant of a previous incarnation rather than the way we tend to use it as a substitute for an individual operating in a different realm. Interestingly, there are also elements of Western culture, notably the focus on the four elements: air, earth, fire and water, in contrast to the five Chinese elements, earth, fire, metal, water and wood. The stories are set in an imaginary world, which I look at in more detail below, with tribes that are associated with one of the four elements. Each tribe has 'benders', people who can manipulate their particular element for defence or offence. Those bending different elements use different martial art forms: for air it is Bāguàzhǎng; for earth it is Hung Ga kung fu; for fire it is Northern Shaolin kung fu, notably with projecting kicks and for water is it Tai Chi. There is reference to a person's chi (in Japanese ki) being able to keep them warm.
Each generation an avatar comes, a person with ability to manipulate all four elements, though originating in turn from among one particular type of people. S/he is also able move into the spirit world to speak with the various spirits who control aspects of the world. Whilst this seems somewhat like Shintoism, you have to remember that in the West, especially in Classical epics, heroes went into the Underworld to speak with the dead or the as-yet unborn. In the movie and the television stories, the current avatar is Aang awoken from where he was frozen in ice. He is the sole remaining airbender following the massacre of all other airbenders. The key antagonists are the Fire Empire, with steampunk technology, and populated in the movie by people looking like those from our Indian subcontinent. The earth people appear Chinese; the water people are Anglo-Saxon/Nordic in the South living like Inuit and in the North like Russians or Swedes of the 18th century and the air people, of whom we only see monks and nuns who are airbenders seem to be Tibetan or Khmer, as their culture seems Buddhist; this is poignant given that Aang wanders passed numerous shallow-buried skeletons in the movie in a location looking like Angkor Wat.
As to the movie's story being too complex, I would say if it can be followed by a 9-year old, then it is not overly complex. Basically it is as follows: the Fire Empire wants to conquer the world; a boy with powers is revived and helped by friends to gain powers; a son of the Fire Empire ruler tries to capture the boy to win back the affection of his father; both this son and the avatar are opposed by a power-hungry general; there is a climax in which the avatar beats the Fire Empire forces besieging a city and the emperor's son escapes, so setting up events for the sequel (this is supposed to be a trilogy). The special effects are fine and are certainly as good as anything you would see in the 'Narnia' movies, in fact, used in a more imaginative way. I think the key thing which upsets reviewers, especially in the USA, is that 'The Last Airbender', like 'The Golden Compass' (2007 which has people's souls manifested as animals) and 'Percy Jackson and the Lightning Thief' (2010 featuring a demi-god son of Greek god Poseidon, growing up in contemporary USA) draw from concepts outside the Anglo-American interpretation of the Judaeo-Christian approach. The Narnia movies (2005-10) and 'The Lord of the Rings' movies (2001-3) laud and even the Harry Potter movies (2001-11) appear to fit into. In many ways these other movies bring a refreshing approach to fantasy rather than rehashing very tired concepts, yet that seems to open them up to harsh criticism, judging them on a different basis to fantasy movies from the kinds of contexts that so many reviewers seem to feel are the only acceptable ones.
'The Last Airbender' is certainly far from being Shyalaman's nadir and in fact even as an adult I am interested to see what happens next, but I fear no sequel will never be made as too many reviewers have done a good job of burying this movie as they did 'The Golden Compass'. I do also think that many UK-US reviewers have an issue with movies in which Asians are the lead characters; they have to be either poor people eliciting sympathy as with 'Slumdog Millionaire' (2008), comic characters like Jackie Chan's roles in Hollywood movies or the baddies as with Jet Li's roles in movies he has made in the West. How long that attitude will be permitted in a world in which China and India wield such economic might remains to be seen.
Anyway, setting aside my view of the movie, I was interested to see what the world featured in 'The Last Airbender' looked like. Maps of this world, for which I can find no name, feature in the movie and I was able to find a number online shown below. Doing a search I found a number of interesting versions from a website called 'Deviant Art' but I avoided those as it seemed to be something pornographic and I worried that in some perverse way this setting was being suborned for inappropriate uses.
Maps of the World of the Elemental Benders
This one shows the different elements bent in the different regions. Red is the Fire Empire, blue are the water nomads, beige is the earth regions and white are the air regions, though from what I know of the story all but one air bender has been killed, I assumed along with many of the people of these regions. The water regions are polar, the other areas temperate or tropical.
These maps show us locations appearing in the television series and the movie. The Fire Empire laid siege to Basing Se for 100 days without success and in the movie goes to attack the main city of the water tribe of the North, but is defeated due to the intervention of Aang the Avatar who by this stage has mastered water bending in addition to air bending.
Looking at these maps we see classic elements of fantasy worlds which I discussed at length back in 2007-8. There are the compulsory inland seas at the centre of the main continent. Other features remind me of other fantasy locations. The Fire Empire reminds me of Melnibone in the Elric series by Michael Moorcock: http://rooksmoor.blogspot.com/2007/08/atlas-of-imaginary-worlds-3-islands-and.html The two polar regions look like distorted versions of Antarctica in our world. Seeing the movie, I had wondered if it was set on our world in some distant future after significant geological changes. We see a strange flying rodent creature large enough to carry people, reminiscent of the animal that carries the hero in 'The Never Ending Story' (1984) and there is a lemur-bat creature reminding of some of the envisaged evolved creatures in 'After Man: A Zoology of the Future' (1981) and the other similar books that followed. The landscapes are pretty varied something the movie makes good use of and it is often difficult to tell when what you are seeing is not part of New Zealand and where it is CGI-generated, especially with the air monasteries. This is an interesting fantasy series which adds another fantasy world to the canon. In my view, if you have a child 11 or younger, ignore the view of the critics and rent the movie on DVD; you may find that, like me, you pretty much enjoy it too.