So basically what we've got here is a very predictable hollywood film with some 3D effects added to give it an extra boost. The film itself, is good enough to keep you interested, I mean it's not awful, but it is predictable, that doesn't mean it's not entertaining though. It's a popcorn flick with some fringe benefits.
I saw this in standard 3D which at a whoping $16.00 a ticket, was a rip-off. For some reason, seeing it in 3D made the screen look smaller. I also seem to remeber 3D poipping off the screen a little more when I visited Disneyworld as a kid. There were two films I've seen in 3D, a demo flick Disney used to run, that featured a bunch dream sequences with a bunch of kids in a field, on a carousel, flying. The other was Michael Jackson as Captain Emo. Personnally the most memories I have of 3D are of the demo flick. The kid blowing danilion seeds all over the place, they seemed to scatter all over us. My point is that this didn't seem to be the case in Avatar. Sure, a tail or a wing would pop out here and there, and there was a nice jungle scene where Jake first meets the girl and follows her through the woods, yeah, that was cool. but as a whole it left me wanting more. See this bit in I-Max if you can.
The animation was good, it looked real enough so that I wasn't constantly thinking how fake it looked.
Just because it's the highest grossing film, doesn't mean more people saw it. It costs more than twice as much to see it as E.T. cost (around $7.00 if I remeber correctly) So double the price and you gross more.