What everyone thinks: It was game-changer; the special effects and 3D were great. When Avatar came out there were people saying on message boards they wanted to kill themselves because they could never actually visit Pandora, the world from James Cameron's sci-fi. Not only does that show how the film's environmental message was clearly lost of some, it highlights just how massive the film was. A box office behemoth whose only potential equal may be the return of Star Wars, it completely captured audience's imaginations. The special effects were touted as decades in the making and 3D, a gimmick previously reserved for animations, was meant to be the best yet. If that all sounds like marketing spiel, it's because it is. The real reason it's good: James Cameron is a good storyteller. If staring at pretty landscapes was all audiences wanted then it'd be Koyaanisqatsi that was the highest grossing film of all time. The stereoscopy in Avatar certainly worked better than in the subsequent spate of cheap conversions (think the cut-outs of Clash Of The Titans), but it was still serving as a gimmick, not an artistic tool. And while people may have been brought in on the promise of ground-breaking effects (that aren't that beyond the internet standard) what got them staying was the actual story. Avatar certainly isn't the most original story ever told. But it's presented in a mature yet accessible way that gave it a wide appeal. As with Titanic James Cameron understood the broad strokes of blockbuster cinema and made something immediately crowd-pleasing.
