Superman has had many variations over the years. From the original Golden Age hero, who was simply a really powerful human who had only kryptonite as a weakness; to the Silver Age version, the one most remembered due to the sheer unlimited nature of his powers; to the more recent versions, which try to put biological limits on his abilities.
One of the things I tend to like about Superman is that he can be a character with limits and no limits. His being limited allows for stories where beings are more powerful and Superman can show his boundless fortitude. Having no limits allows for some pretty badass escapist fiction (though I admit, this version worked better in the Silver Age when storylines didn't carry over for more than two issues at a time).
Ultimately, what I love about the character (besides that he's a journalist) is the moral code of the character. Superman could overthrow the planet easily if he had wanted to, other heroes not being taken into account.
As such, it really speaks to who he is as a person. Clark Kent's family life and background is the basis for Superman's moral code more than his Kryptonian background, which is why Clark is usually played as the main character. The best Superman stories are about the man - how he responds to stressful situations, is tempted but ultimately comes out stronger.
One of the reasons SuperCena doesn't work in WWE is because he takes his adversity like a joke and puts down any threat as trivial. They miss the point. Superman isn't beloved because he destroys barriers like tissue paper. He's beloved because of the limits he imposes on himself and refuses to break no matter how difficult it makes his life.
And I would be doing a disservice to not mention Lois Lane. Lois has evolved through the years from the cut-and-dry damsel in distress to a true hero in her own right. She's the best journalist on the planet and will willingly throw herself in harm's way to get a story for the public.
Superman keeps Lois from becoming too full of herself (her ego is seen in many stories), and Lois helps Superman push on with his mission even though he's made it so hard for himself. I don't mind Superman-Wonder Woman as a couple in the New 52, but I feel it has to be temporary, as the two simply don't match with each other the way Lois and Clark do.
I got into Superman through reruns of the old George Reeves series and got much enjoyment out of the first two Christopher Reeve films. I didn't mind Superman Returns, but it wasn't to the level of its spiritual predecessors. And although I haven't watched the full series, pretty much all TV adaptations of Superman besides the original have been pretty awkward to sit through.
Comic-wise, I'll count down the best Superman stories for you all some time. But for quick recommendations, Superman Birthright is the best Supes story ever in my view, Superman: Red Son is the best elseworlds story, All-Star Superman is a great combination of all that has made Superman great over the years, and What's So Funny about Truth, Justice and the American Way? (Action Comics #775) is the best individual Superman issue across its monthly titles' histories.
Happy Birthday to the original superhero couple. I look forward to the day that Clark escapes the friend zone and we can get back to the tension that made the early series so fun to begin with.
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