First of all, he gets humanity. It may have taken him a while to get past the idea of a race who are stuck with one form for their whole existence and who can only communicate verbally, and thus, lie, but we're all carbon-based, we share a dependence on the same star and on water; given the decades that J'onn's been here, I think it's safe to say he generally knows how any single human being ticks without even having to peek into his/her psyche. So he's not a whiner or an armchair philosopher by nature. Now, while he understands human nature, that doesn't mean he likes it. Considering how the First World (i.e. the Man) treats, well, brown people across the world, as a green guy, he hates racism, tribalism and all forms of factionalism, across the board, in almost the same way that an adult with no children hates to hear a toddler complain about being denied his favorite flavor of yogurt. The Martians were an ancient race that had hit a plateau thousands of years before J'onn was even born (btw, he's probably around 500 years old in the way we reckon time). The Pale Martians that attacked Earth at different points in the past would be, to J'onn, like Alexander the Great coming back to life, commandeering NATO and taking over the Northern Hemisphere... he knows his people when he sees them (feels them, scans them, whatever), but he was still taken aback by his own ancient history walking back into real life. Anyway, the Martians as a race, by J'onn's time, were as united as independent sentients could be. They'd evolved past ideological divisions, past expansionist interstellar colonisation. Had the plagues and fires not done them in, J'onn's people would have faded quietly into the red sands before humanity's first ships arrived there. That's where Professor Erdel's retarded super-telescope comes in.
J'onn had just bid his family goodbye as they and a handful of the rest of the Martian population fled into what we call the Phantom Zone when he was transported-- through space AND time, mind you, because when J'onn last set foot on Mars the Earth was like a fascinating nature preserve to them, with a global human population of around ten million-- to an observatory just outside of Denver, Colorado in early 1960. There's something dreadfully wrong with that picture and if J'onn ever found out what, he certainly hasn't mentioned it to anyone. Think about it: Professor Erdel was somehow so bad at repairing a radio telescope, he turned it into a remote-controlled time-laser. It's like Forge got hit on the head with a bowling ball Fred Flintstone-style and started turning Cerebro into a bong. Er, anyway.
Following that I imagine the events of The New Frontier (minus the JLA who didn't appear til decades later) happening for J'onn- trying to fit in, mixing it up with King Faraday and the OSS/CIA, all that. But afterwards, I don't see him trying his hand at being a superhero-- at least, not often. I like the look of a green guy in a black suit-- J'onn B'ond, if you will. I can see him working as a spy for American interests throughout the '60s and '70s, up until the resurgence of supercrime that presaged the arrival of Superman. Once he appeared and the story of Krypton got out, J'onn saw a new way to be of service to his adopted world. And yet, that's not half the story. J'onn has traveled all over the Earth dozens of times, not always in service to the US. He made a good show of things for the brass in Washington, but he's been a spy for every side in every region of the world. He has dozens of identities, hundreds of contacts. It's how (as I stated above) he's grown to understand humanity so well. After all, we often forget that he's as fast and strong as Superman, as clever as Batman and as dedicated as Wonder Woman. While Detective John Jones is the identity he settled into during the Silver Age, he keeps up appearances in other hometowns around the globe, gathering information and occasionally letting the US (or Chinese, or Venezuelan, or Egyptian, or hell, the Vatican) government put it to use. Why? Is he playing all of them against each other? Using them for his own inevitable power play? It may seem that way sometimes-- cynical. Machiavellian, even. But those adjectives don't really stick. The worst word you could apply to J'onn, and this is when you really want to stretch the truth, is patronizing. He views short-lived, short-sighted, good-intentioned humans as needing protection, as well as guidance, while they work things out for themselves (at what seems like a glacial pace to a culture of telepaths who can figure out in an hour what's best for society). But really, all that that means is he's fiercely protective of a species he knows hasn't reached its full potential yet. If he could give every human the "powers" native to every Martian, he would in a heartbeat.
The fact that he's able to open his heart and mind to humanity at all in the face of his losses-- wife, child, homeworld-- is admirable. That he puts his life on the line for us every day, and is as famous and beloved in the Southern Hemisphere as Superman is in the USA is astonishing. That he still finds time to volunteer at homeless shelters, to share Oreos with children awaiting flood relief, and to rent movies with the shut-in woman across the hall in his building once a week, is mind-blowing. Like a D&D elf, he doesn't need to sleep, at least not nearly as much as humans-- an hour or two every hundred hours just about does him.
Fire is still a problem. I hate that J'onn's vulnerability to it varies from writer to writer about as much as a vampire's vulnerability to it. So how about this: Martians fear fire in the same nearly-unshakeable way that 21st-century humans fear the very mention of the phrases "nuclear warhead" or "weapons-grade uranium." And as far as naturally-occurring elements (in the ancient definition I guess, as opposed to the periodic table definition) go, again, it's about as rare. Mars's atmosphere is 95%(ish) CO2. Fire can't really exist for long there. Lava and lightning were about as close to fire as any Martian was likely to ever see. Martian culture evolved without fire-- as beings who can control the very shape of their minds and bodies, including nerve endings, they were able to control the thresholds at which they felt "heat" and "cold" as we know them. So while J'onn's physical form can adapt to both flame and radioactive elements (the use of which were a brief and shameful footnote in Martian history), the psychological reaction to fire, in particular, is a bit harder to control and defuse. Kryptonite may physically, literally sap the solar reserves from Superman's cells and render him powerless, but fire robs the Martian Manhunter of his reason, his confidence and his all-important self-control, thus leading some to believe that it literally takes his powers away. Not so. As long as he has a spare moment to collect his thoughts and recommit himself to what he's doing, J'onn can phase through a burning building to save your cat, beat the hell out of Heatwave, whatever. But he needs that spare moment, and if a resourceful villain knows not to give it to him, J'onn's going to spend a few minutes as a green, telepathic puddle.
So, to sum up: he's not the green, half-naked Superman/Batman/Wonder Woman fill-in. He's best used as a spy and/or tactician-- not because he's not great in the field, but as long as we've got Superman and Green Lantern out there, let's have someone in the background who's smarter than either of them coordinating their assault with what Batman's just figured out back in the lab. He does a lot of what Superman and Wonder Woman and GL would call "dirty work" or "spying" and what Batman and Green Arrow and Black Canary would call "necessary" or "research." On Earth he quickly learned how to hide. He reconciles the telepath (who feels sullied by lying) with the shapeshifter (who instinctively knows the value of camouflage) as he uses his human identities (he never calls them "disguises") to learn more about the human condition. He understands people, he likes people, he's good with people-- but the distance he feels from them (compared to fellow alien Superman) is the difference between "across the river" and "across the ocean". He was raised somewhere else. Had a family and a career somewhere else. And now he hangs out on a planet of smelly, murderous apes a good two feet shorter than him who can't communicate clearly to save their lives and are never more than five minutes away from turning on him and any other alien (or human) not as attractive and congenial as Superman. But he wants to close that distance. He believes that it can be closed just as the gap between any two humans can be closed. He wants Earth to be a little more like Mars. Is that a crime? J'onn doesn't think so. And after all, he's a detective.
Like Cooper in Twin Peaks, but more believable.
