I liked John Carter, but having never read Princess of Mars, I kept drawing a blank whenever I heard the name. Now I'm working on reading the book :) and can hardly wait for the DVD. Having seen the movie, "John Carter" makes sense as the name, but a title is supposed to draw in people who haven't seen it. Unlike "Tarzan," which was exotic (while being easy to pronounce), "John Carter" is too ordinary. It's a title for a biography.
"Princess of Mars" is slightly hokey, but then, so is "Star Wars" - and look how great that turned out! :)