WARNING: MAJOR SPOILERS AHEAD
Batman is an unparalleled hero. His tragic beginning leads not to a desire for vengeance, but a desire to protect a city and the people in. His wealth is not lent to exuberance and frivolities, but resources and investments offering monetary return. His stature is not used for for public advancement, but sacrificed to distract his enemies from the possibilities that the ones he loves are associated with the caped crusader. It is easy to see why people love and admire Batman from an ideological standpoint alone. While other DC heroes may hold similar ideologies in some fashion or another, no other hero has aged as well as Batman, whose very essence seems to flow with the time and cultural interests. Add in the twisted villains, goofy gadgets, and lovable ensemble and it is easy to see why Batman appeals to so many people.
The sales certainly reflect this. In fact, in recent years the title has always been a top five seller of the month in natural sales (natural sales excludes loot crate inflation), and the series has yet to receive a renumbering to boost the sales like the Marvel series that it frequently outsells. What makes this work?
Well, it is impossible to objectively say that a book sells well for one reason in particular. Batman exists in a perfect storm, where the movies have paved the way and video game representation is also solid. But what about Iron Man? Tony Stark is more beloved than he has ever been thanks to the MCU and Robert Downey Jr. If external representation is what drove the characters, then Iron Man would likely sell better than Batman, but it doesn't. So we know external factors won't push a book to the success Batman is having. Is it marketing? Even if the answer to this were yes, you would have to ignore the fact that Marvel practically owns half of the comic book websites, and every Marvel film naturally doubles as an advertisement for their print counterparts.
Still, Marvel cannot create a book that consistently sells more than 100,000 copies after ten issues. In fact, the only book from Marvel to come close to Batman after passing 15 issues ,without using crossover or event gimmicks, is Superior Spider-Man which sold roughly 80,000 copies a month after 30 issues. There is a lot that can be inferred and assumed from this fact, but as a comic journalist, it is beneath me to make wild conjectures... Just kidding. Wild conjectures is the foundation of "comics journalism," so away we go.
What makes Batman so successful? Well let's start with the creative team and how they approach the story. Snyder's background is largely horror based with his most successful titles being American Vampire and Wytches. Snyder takes his strength and applies it to Batman. This is apparent in the foes which Wayne takes on which is expertly and horrifically drawn by veteran artist, with heavy horror experience, Greg Capullo. The backgrounds and capabilities of these two creators blends well so that the story stays true to Batman and plays to the strengths of Snyder and Capullo.
Another key component for the continued success of Batman is the calculated risks. During the arc titled Endgame, a couple shocking things happened. First, it was revealed that the Joker had been alive for perhaps centuries. Did Joker have powers? Was he immortal? Snyder and Capullo stood to change Batman lore forever (or until the next retcon), and they did without unnecessarily redefining the character in a damaging way. It was revealed that Joker had actually found himself a lazarus pool. When he was irreparably wounded, he would take a dip and live on. This revelation not only fits within the Batverse, but explains how Joker, a powerless psychopath, could survive the insanity of Gotham.
The other calculated risk is commonly known as Batbunny. When Bruce Wayne "died" in the finale of Endgame, Jim Gordon took up the mantle of Batman. Being significantly older, Gordon was given a mech-Batsuit. The storyline has since delved into the idea of how Batman's ability to succeed is dependent upon no oversight. Gordon finds himself having to answer to higher ups at times, which restricts his abilities of being the Dark Knight. This is an interesting concept, but it has received two complaints.
The first is that Batbunny would just be DC's Iron Man, a mech-warrior designed primarily for warfare. The complaint was remedied when it was revealed that Batbunny was not a hero, but another gadget in Batman's utility belt, albeit it a very big important gadget.
The second big complaint about Batbunny is simply that Jim Gordon isn't Bruce Wayne. All of those things people loved about Batman, they apply to Bruce Wayne, not Jim Gordon, and for that reason, Bruce Wayne lives. This is the most important choice that Snyder and Capullo have made in the story arc. Wayne is alive, but he is just not interested in being Batman. This means that at anytime, the creative team can decide to bring him back to the cowl. It is a calculated risk which will keep the fans happy without compromising their rights as creators to tell what they feel is the best story possible. This brings us to another reason Batman sells well.
The creative team cares about respecting the fans. To understand what I mean, there are two defining moments. The first deals with price. Multiple times DC has priced, or tried to price, the book at $4.99. Whenever this happens, without fail, a story will come out saying that Snyder and Capullo are fighting that price-point. Why? Because that's a lot of money for twenty pages of story and six pages of advertisements, which should be lowering the price anyways. And advertisements is the second example. When DC told creators to expect paging splitting advertisements, Snyder and Capullo fired back within their story, mocking the decision.
Yet, oddly enough, it must be acknowledged that DC, whether supportively or with resistance, has allowed Snyder and Capullo to do what they please in these books. If they hadn't, the team would have walked long ago, and I'm sure Marvel is salaciously waiting with open arms and blank checks for the duo. The other important choice DC has made is allowing the monthly release. Marvel is all too happy to push their top titles out on a tri-weekly basis, and often there is a lack of quality because of it. The monthly schedule of Batman gives the team an extra week to truly perfect the book in its aesthetic, a vital part of Batman.
The Big Two should really begin to examine the method of these two. The way they work has been successful financially, largely thanks to the story they have provided fans. If Marvel is really all about telling good stories, they will apply some of these techniques, specifically those related to schedules and creative freedom. If DC wants to survive, they'll have to have more writers play to their strengths while taking calculated risks, because Batman is selling well, but not much else is.