I once saw a trailer and found it nice; however, this movie has the disadvantage of being somewhat similar - regarding the plot outline - to avatar : "White man comes to alien races and befriends woman there and saves the world". Sort of.
That plot outline alone was distraction enough for me. If there had been a different outline, I would hve decided to see the movie.
However, I also acknowledge that this series seems to come from a different "age" of SciFi literature. The plot setting of "human comes into alien world and survives and saves the world" (the "saves the world" is meant to be tongue-in-cheek here) was only changed - imho - vie Star Wars - this was in my opinion the very first movie that did NOT place the human protagonist(s) into a special position in a world - instead, Star wars made clear that hjumans were merely 1 in millions of (alien) races.
Seen from this standpoint, John Carter is an somewhat outdated setting, imho.