I went in expecting "Dances with Wolves with Aliens."
But I came away having found more through my 3D glasses. While the woman behind me was annoying, she was often dead on when she whispered "Fantastic!" at various points in the film. Avatar was great.
To me, the key test was whether I was actually drawn into the film to the extent that I actually cared about what happened to the characters in a meaningful way - especially with non-human characters and a wholly alien world. I found that I did. I was immersed. And it wasn't just the special effects.
While several of the characters were absurdly overdrawn (the bad guys in particular), the main character, Jake Sully, was dynamic, moving from a very authentic simplicity at the outset to a figure of far greater complexity by the end. Grace, played by Sigourney Weaver, breathed life convincingly into the storyline as well. While several small questions arose in the plot and the aliens were a little too conveniently humanoid and reminiscent of Native Americans, the overarching narrative was strong enough to succeed. It was Dances with Wolves with Aliens - with the additional compelling anxiety of the Matrix woven into the mix. There are many possible allusions, really, but the whole was something new in the end.
The movie was epic enough to make it into the great category for me. It was surreal and beautiful as the characters breezed through a phosphorescent forest at night. It was harsh and brutal in various battle scenes. It was majestic in its landscape of floating mountains and soaring flights. It wasn't excessively melodramatic or nauseating in its incorporation of a love story. It was more accurate than usual in depicting humans as not much changed several decades into the future. It touched on contemporary issues of Iraq, Blackwater, and terror with a few references, but didn't attempt to overdraw the comparisons. It was actually painful as things of great worth were destroyed - someone aptly referenced the movie FernGully from my childhood afterward (one could argue that the movie has a patently liberal bent to its "message"). And most importantly, it raised enough issues that made me think for a few days afterward, that made me contemplate my humanity for a bit, whether on my own or with friends who have also seen the movie.
There's a good deal more I could say, but I'll simply say go watch it. It's the best movie I've seen in about a year, and I can understand why it's doing well at the box office.