First appearance: Detective Comics #225 (1955)

During most of his comic book appearances, the Martian Manhunter has been the conscience and soul of the Justice League. Despite being the most alien member of the squad, he has had a history of being the most humane participant amongst a team of demigods. Whenever the character is taken out of the League and put in his own comic series, though, Martian Manhunter always fails. And that's why a solo movie for the Martian just doesn't seem plausible. 

It’s obvious that J’onn J’onzz doesn’t have the unique personality of characters like Batman, Superman, and Wonder Woman, but the fact that he also doesn’t really have a compelling cast of villains is what hurts him the most. There are certain popular comic book characters that just can’t make that jump to live-action; we think Martian Manhunter has enough working against him that he would unfortunately fall into that category.