Who is Batman? He is a creature of the dark, a character who fights evil every day and night, and the hero upon which almost all dark comic book heroes (like Spawn) were based. He is a troubled man who lost his parents to criminals, and vowed to stop the deed from being done to someone else. He became Batman. In any medium Batman is a top seller: Comic books, movies, TV shows, and more. He is aptly called "The Dark Knight" by many, which shows his heritage as a creature of the dark. He is second in terms of importance in the comic book medium, because without Superman there might not have been a Batman. But Batman is a far more tragic and disturbed individual than Superman and this makes him the more mature hero. Few heroes battle themselves as much as Batman does, but even when his back is broken or his home city of Gotham is nearly destroyed he proves that he is the strongest super hero. The character is popular because he is such a dynamic character who has been through more trials than any other super hero-whether it be in the DC or Marvel Comics.
This leads into why Batman is so different from other super heroes like Spider Man and Superman: he has no special powers and the night is his home. Perhaps he is popular because people can relate to Batman more than to any other hero. Batman is one of the more tragic comic book heroes ever, and combined with his resolve to fight evil this is the reason that Batman is such a dark but popular hero.
There are other elements to Batman that make him such a dynamic hero. At his core he is a detective who fights on the side of good against many villains. Some of those he battles are the better villains ever imagined in any comic hero's rogues gallery. The nemesis he faces most is the Joker, an insane criminal with a sick sense of humor.
There is also something to be said for the talented writing that has frequented the Batman comics and other media. Take "Batman Begins": In this movie Christian Bale played the character as well as Michael Keaton in the first "Batman," and director Christopher Nolan depicted the Dark Knight as he should be. Jokes were infrequent as had been seen in the previous unsuccessful Batman films "Batman Forever" and "Batman and Robin"; instead Batman was taken seriously and there was a respect for his past as in "Batman." "Batman Begins" was important for fans as it showed the character could still be a top seller in the movie market and everyone could enjoy it.
Instead of summarizing Batman's past incarnations a look into a few of the better storylines should be noted. These stories are considered comic book classics and the reason many comic book fans chose the hero to be their favorite. The best Batman stories are "The Dark Knight Returns," "The Long Halloween," and arguably the Elseworlds tale "Batman & Dracula: Red Rain." There are others, including Alan Moore's "The Killing Joke" and Frank Miller's "Batman: Year One." There were also the hit storylines "No Man's Land" and "Knightfall." Instead of going into detail on each perhaps it would be best to state why some were so popular.
"The Dark Knight Returns" showed Batman at an older age retaking Gotham city, and made Frank Miller a legend. "The Long Halloween" was Batman at his detective roots, and popularized writer Jeph Loeb. Lastly "No Man's Land" was the longest running of all these storylines, and for good reason. It depicted the Dark Knight fighting both mother nature and just about every villain from the Batman mythos.
Batman has more quality stories to his name than any other comic book character. There are many other comic and graphic novels that made Bruce Wayne the legend that he is. Batman writers and illustrators were responsible for the addition of high-drama into the comic book mythos. "Batman" was not the first super hero film to hit the big screen with success, but at the time it was the best comic book based movie ever. Now, with "Batman Begins" success and "The Dark Knight" sequel film coming, the hero is stronger than ever.