Avatar was not a film with a powerful and meaningful message. It was, however, an excellent technical film - that is what got my interest. Cameron uses the cutting edge of technical cinema, and uses it well, and that advances the story telling possibilities of cinema. Even Titanic (which was a phenomenal bore) used the most advance technology at the time.
Plus Avatar was great escapism.
I thought it was pretty obvious going in that Avatar was just a vehicle for the effects. I was actually pleasantly surprised, not by the depth of the story, but by the depth of the world and culture of Pandora. The movie was a display of technology and graphic design and, when viewed as such, it is excellent in my eyes.