It's because the Avatar movies are more popular with the non-nerdy crowd. They're like, fine, but people that watch a lot of movies, play a lot of video games, etc have seen the plots and spectacle before so they're not that impressive to them.
People that haven't absolutely LOVE the movies because the presentation draws them in more. I have several older relatives that like, primarily watch game shows, reality TV, and/or non-fiction that absolutely love Avatar and have rewatched each like 3-4 times when they NEVER do that for anything.