This is how I would write Martian Manhunter, if given the chance to revise his origin...
The story starts off with Martian Manhunter on Earth, not long after he had been teleported. Due to an imperfection in the teleportation device, he suffers from major amnesia and remembers little of his Martian life, other than a few vague and disturbing images of the planet being consumed in flames.
He manages to figure what is going on, and so decides to try and blend in until he assure a safe return to Mars. After seeing the Word committing crimes (another character I want to reinvent/improve), he finds himself compelled to follow these weird and strangely interesting criminals or 'supevillains' that seem to be swarming Earth.
As a result, J'onn J'onnz takes on the life of John Jones, a man on the verge of losing his office bound detective job.
Frustrated by the case of the 'Human Flame', and the lack of progression that comes with it, he decides to take a sheet of paper home and make an origami crane every day, saying how he likes making something plain into something beautiful; making something new from something seemingly insignificant, a rather strange analogy of himself, and overall, the Martian race.
After a few years getting nowhere chasing the fire based criminal, he comes home to find that his apartment is covered in origami cranes (1000 to be precise), without him realising how many were made. A lot of work goes unnoticed. No one even cares about the missing paper.
He returns home from work one day, only to find that his apartment has been set on fire in a similar manner to the human flame's MO. Nothing remained, but the ashes of his hope and memories. He spends the night in the police station and gets a visit from a younger Jim Corrigan (still in his days as a detective, not long before he died), saying that they had managed to catch the Human Flame and that he was ready for interrogation, but that he had some other things to attend to (a nod his origin as the Spectre).
John Jones jumps at this chance and enters the interrogation office, talks to the Human Flame, finds out about his motives and nearly kills him after taking it to a personal level, despite him being insistent that he didn't burn any home covered in Origami cranes. This sparks the Human Flame's vendetta and hatred of JJ. As a result of this abuse, he was later fired from his job as a detective and thrown out onto the street, penniless, jobless and homeless.
Within weeks, thinking himself to be the last Martian alive, he is shocked to find that another Martian is on earth, going by the name of 'Fernus', and is making constant public appearances in the attempt to help prevent the human race from failing in the same ways that the Martians did. However, JJ is convinced that this Martian has some connection to 'the Burning', a race that sparked the Martian's phobia of fire.
He later comes head to head with Fernus, who is revealed to be JJ's fire obsessed split personality that plans to take revenge on Earth, the ignorant people that abducted him and has since ruined his attempt to be normal. He took inspiration from the Human Flame and essentially replicated his attributes, all of which he knew through John Jones's thorough detective analysis of him.
He thus adopts the new super-heroic persona, the 'Martian Manhunter', feeling that it is his duty to assure the safety of humanity....
Anyway, this is just an idea.... feel free to comment or suggest anything!