1.) Avatar - Even though JCM is an older and beloved story by some on film it's a different animal and very much like Avatar, but released after Avatar making it a copycat of sorts. As bad as it sounds no one knows who JCM is which made the film seem like even more of a copy of Avatar.
2.) Poor Marketing - Avatar (yeah I'm back on that) started promoting the film heavily for months before the release. I mean I remember when the first teaser trailer was shown on the largest Jumbotron in the world at the then newly minted Dallas Cowboys stadium.
3.) Unknown Cast - JCM had an unknown actor in the protagonist role and wasn't marketed at all until about a month before the release, unless you call ads with a black and red logo in limited visibility publications marketing. Even among hardcore ERB admirers John Carter was unknown...the most commonly accepted look for the character is as a guy with short hair: (picture below)

The short hair is pretty important at the beginning because Carter is supposed to seem out of place. He's not sure whether what he's experiencing is real or a dream, but he's definitely not originally from that world where a hair cut is pretty hard to come by.
The film actor basically looks like a slightly bigger version of the long-haired hippy kid of the pastor in "7th Heaven."
4.) The Color Palette Isn't Good - Mars is Red, everyone knows this. In the JCM film the planet is very desert like, which makes sense, but it's yellow/biege so I doubt very many people draw a favorable connection between what they know Mars is and the environments that are seen in the previews of JCM. Even among Sci-fi and/or Sci-fi art enthusiasts it's more likely the environments will draw a comparison to something like DUNE and Tatooine in Star Wars before Mars. The Martians are stereotypical color "Green Aliens" but they still don't look like the aliens most people are accustomed to seeing that are creepy, edgy and don't talk. Again, because the art direction took the characters in to the tall, lean and lanky direction there's going to be a natural inclination towards comparing them to everyone's favorite cool blue aliens and well JCM movie Martians just come out looking puke green. Frazetta's depiction of the Martians in JCM probably wouldn't translate well straight to film they were quite beefy, so that was probably a bad choice.
So that's my take. What's yours?





