the sets were incredible and the visual effects were great but everything else fell flat completely.
Sounds a lot like the other Avatar movie.....
Nah, It's not that bad, really.. Avatar (the blue one) was a rather standard story which was executed in a rather good way, although the focus was a tad too much on the graphics side. But I didn't notice any major 'film-breaking' flaws.
I get the feeling that all of James Cameron's movies are like that. The Abyss was also very cliché at the end which was a film-breaker for me - I watched the Director's Cut, the version with the Aliens), but the acting was awesome. I have never seen Titanic, but apperently, that is a cliché Romeo and Juliet story as well, executed in a rather good way, although the focus is a tad too much on drama.