Exactly, Avatar was literally what I was picturing when I wrote that. They're not good movies. But damn they're fun to watch in 3D, on a giant screen, and with great sound.
That's not to say that all movies in this category are *only* worth watching in the theater like Avatar is. For instance I would have still enjoyed the recent Dune movies either way but they were a lot better with all the pomp & circumstance.
At that point what you are describing is a theme park ride. It only works a handful of times though before people get bored of it and want something else.