Astro City: The ordinariness of the extraordinary.
Multi-issue arcs tend to have their own central themes as well. Confession, about a sinister superhero training a sidekick while public opinion turns against supers, is about doing the right thing regardless of what people think. The Tarnished Angel, a noir mystery about lowlife supervillains being murdered, is about shame and the hold of the past.
The Authority: How far are you willing to go to make the world a better place?
The first three series of Batgirl each have three different overarching themes:
The 2000-2006 series featuring Cassandra Cain is about innocence and redemption; specifically, about how innocence can be corrupted and what is required to redeem someone for the wrongs they've done in the past.
The 2009-2011 series featuring Stephanie Brown is about heroism, and what it takes to be a hero even if no one else thinks you're capable of it.
The post-New 52 series (2011-2016) featuring Barbara Gordon is about healing the wounds of the past, whether physical, emotional or psychological.
Batman: How the traumas of the past affect the choices we make, and thus how they shape us into the people we are in the present.
In particular, practically every member of Batman's Rogue's Gallery either reflects a part of Batman himself and/or like him has an over-arching trauma that has shaped their lives ever since — except where he has used his trauma to make himself a better man by defending the innocent and trying to prevent what happened to him from happening to others as much as possible, they have succumbed to despair and evil, and use their traumas as an excuse to hurt others.
Ex Machina: Do the ends justify the means? And, does anything ever really end, anyway?
The Flash: The Return of Barry Allen: The need to move on from the shadow of your hero and becoming one in your own right, all while honoring your predecessor. Best exemplified in the conflict between Wally West and Eobard Thawne. Wally must learn to move past the shadow of his late mentor Barry Allen. Thawne, on the other hand, wants to be Barry Allen, and when that doesn't work, he decides to destroy everything he stood for.
The work of Geoff Johns frequently revolves around themes such as family, managing your emotions, and finding your place in the world, with the theme corresponding to the overall motif or theme of the character(s) he's writing for. For example:
His Green Lantern run spanning pre- and post-New 52 revolves around overcoming fear and accepting your emotions.
One bad day can drive a normal man to madness, but we have the choice to stay sane even when confronted with tragedy and suffering. Truly evil people are often convinced that everyone is as bad as they are and will go to extreme lengths to prove it. That doesn't make it true.
Can you actually help the mentally ill by treating them? If you can't treat them and if you keep them alive knowing they will keep killing, can The Hero be considered saner than the villain who realizes the absurdity of the situation?
The Sandman (1989): All things change, all things end. Neither of these are terrible. And there is always more to everything (and everyone) than you expect.
What it means to be a hero, a good person, and an inspiration to others — and how these three qualities are not necessarily the same.
One doesn't need powers to make the world a better place, just the will to do so.
Brain beats Brawn. Every time. Superman, despite his reputation, more often than not has to rely on his quick-thinking and creative applications of his powers to fight and beat enemies. The real drama comes from how many people get hurt before he can find a way to end a fight passively.
The complex nature of identity—secret or otherwise. The writers have gotten a lot of mileage out of exploring the fact that Superman is essentially three different people: "Superman" (a superhuman crusader for truth and justice), "Clark Kent" (an unassuming journalist from Middle America), and "Kal-El" (a tempest-tossed refugee from a dying alien race). There are many different possible interpretations of which of them—if any—is his "real" identity...which is kind of the point.
Transgenerational trauma. Superman lives with the knowledge that he and his cousin are the Last Children of Krypton-– an entire planet with millions of years of history, billions of people, and all the potential it had, completely gone. Worst of all, it was a tragedy that could've been avoided. So, he's resolved to never let that level of loss ever happen to Earth, or anyone else.
You Could Have Used Your Powers for Good! and Upbringing Makes the Hero are major themes for Superman's rogue's gallery, and how they are dark reflections on the Man of Steel himself. His enemies have all lucked into abilities that set them apart and above regular people, but generally only utilize them for selfish and petty reasons because they literally can't see beyond their short-term desires. No one deserves power, but what one does with it is the true test of character; Superman is the Man of Tomorrow because he uses his gifts to help others, while his adversaries are very much People of the Past because they only wish to prop themselves up over others.
"For the Man Who Has Everything": Disillusionment, and the choice between embracing a lie and confronting a painful truth.
New Super-Man: Balance, be it between western and eastern systems of values, progress and tradition, focusing on the past and focusing on the future, detachment and emotion or strength and weakness.
Swamp Thing: What makes us human? Is there a part of our humanity that will not disappear even if everything else is taken away from us?
What would inspire someone to dress up in an elaborate costume and fight crime as a vigilante outside of the fantastical world of comic books.
Also, explicitly: "Who watches the Watchmen?" (Who protects the people who protect us? And if they go wrong, how will we know, and who'll protect us from them?)
"Who makes the world?" When even a Physical God doesn't have all the answers when the "world's smartest man" is filled with doubt and the Presidents and businessmen are equally confused, why do ordinary people keep believing that they are more powerless or that they need heroes?
Do the ends ever justify the means? Is sacrificing a ton of people for “the greater good” ever right?
Wonder Woman: The conflict between the desire for peace and how it may be sometimes necessary to fight in order to ensure it.
