Only seen this in 2D. Impressive CGI and big budget etc but was really rather boring on an emotional level. Like a rollercoaster.
Best American film recently (IMO, obviously), Synecdoche New York. It's about life, death, illness, insignificance, recursion, dreams, time, relationships, desire, power, art, lots of stuff.
General rule of thumb...
Entertainment = distracts from the human condition (a greater meaning/significance, and ultimately, our own mortality)
Art = Confronts the human condition. More effort but ultimately more rewarding.
We need both in the world but if I want entertainment, especially from Hollywood/US films I'll choose comedy as some are pretty good. Burn After Reading was a recent good one, Men Who Stare at Goats less so but still funny in places.
One US film I recommend which is both funny and moving (without going over the line into the sentimental, a rare thing) is Box Of Moon Light, a 90s film that went under the radar at the time but is well worth seeing (John Turturro and Sam Rockwell are in it.)
I won't be watching Avatar again, well, perhaps I'll watch a bit of it some years in the future when it's on TV at Christmas and I've eaten or drunk too much and can't be bothered to do anything else (I think they should include this final paragraph as a quote on the DVD box.)