I think people go to movies for all kinds of reasons. The bigger gauge of how well a movie is liked and appreciated by the audience, versus people just going because they've been herded along like so many aimless cattle by a massive marketing campaign and peer pressure, is how many go back for a second showing or more.
I think Avatar had, and still has, a pretty big re-watch factor. That certainly contributed to the boffo box office. And that usually means it was a pretty good movie, too.