I think Avatar's high ratings are completely earned. It is one of the best stories on TV, period, and when it comes to thematic depth and anything approaching a moral code worthy to strive for, pretty damn unbeatable, I'd say.
I agree people should have been watching it long ago, but Nickelodeon never know what to do with this property. It was too weighty and good for its home, and you were never going to get mass watching with the show consigned to Nick's site, with ads.
Now, I can sing praises of the show and not have to suggest some weirdo anime streaming site when people ask me where to watch it. I expect it'll get significant traffic in the coming months.