It might be another Batman Begins and The Dark Knight?
Before BB came out, I'm so excite to see it(like Avatar), because I love Following, Memento, and Insomnia is not bad. But BB is so bad and boring, yet the sequel TDK is amazing.
I enjoyed Batman Begins' story. The movie was never boring (saw it twice in theaters). Sure, it does take an hour to get to the Batman stuff and sometimes when I watch the movie I just want to get straight to the "good stuff" aka the Batman stuff, but that first hour isn't all that boring and I can still sit through it. I'd say the action scenes are more of a problem than the movie's story/pacing, although I've watched Batman Begins so much that I can understand the action scenes and figure out what's going on.
I didn't mind the story to the first Avatar movie. Everything has been done before. It's just the filmmakers' job to repackage stuff and tell things in a different way. That's all Avatar did. Also, I gave Avatar's story a pass since back in the day, I only saw one or two movies with the same kind of story, although I still haven't gotten around to watching the other ones people compare Avatar to. But everything has been done before in some capacity. It's just up to the writers or filmmakers to repackage it in a different way. So in a way, expect Avatar 2 and the other Avatar sequels to borrow or "steal" stories/plots of other movies. Everything has been done before. And if you think Avatar committed some crime, how many different versions of the Scrooge story do we need? We get one or two new versions of A Christmas Carol EVERY Christmas. Or how many biopics of Princess Diana do we need? Since her death, we've gotten one/get one every 2-3 years whether it's a theatrical movie, a miniseries, or a Made-For-TV movie. About enough of that. And she hasn't been dead that long (well, at the time of this comment being written since someone could be reading this comment years or decades in the future). So the type of story Avatar has hasn't really been done too many times compared to some other types of stories/biographies.
If he wants to meet with the same success as he met in the original movie, then he's going to need to start doing promotional blitz like he did with the original movie. I've yet to see anything about it other than what's posted on this website.