Batman as Wish FulfillmentIt's been stated that Batman as a hero has never grown stale or supposedly never has anything to worry about and will always be the fan favorite (in some circles at least). This always bugged me on just why fanboys consider batman to be so great. Finally, a solution was found: Batman is an airtight form of wish fulfillment that doesn't age in our current cultural context. Batman is Badass Normal. Already he's fulfilling the realistic wish of so many. We know we can't fly or aren't super strong or super fast. Batman though is a hero that supposedly, "could be you or me." (from Batman: Unmasked) He's our projection of accepting our limitations, but still reveling in how far we can take it. Second, Batman has the whole Dark Is Not Evil and Good Is Not Nice bent going for it. Mankind longs to be good, but at the same time we applaud the swift and brutal defeats of those in the wrong. Batman does both of these things, and yet still remains a good guy for not crossing the Thou Shalt Not Kill line in modern times. Third, Batman is the paragon for our love of cunning and intelligence. True, he doesn't exactly have an alien encyclopedia, but the notion of being Crazy-Prepared for the future in the chaos of real life is extremely appealing, and Batman can somehow do it without seeming silly or having Fan Dumb screaming Ass Pull. Fourth, Batman is our selves rising above reality. Batman lost his parents at a young age, but sought to go forth and create a new order no matter the personal cost. This is extremely admirable as not only has he moved forward to higher causes, but he's doing it in a manner that we enjoy watching. (Heck, his charitable work as Bruce Wayne is practically a footnote compared to what Batman has done, but perhaps that's just the way comics work) Fifth, Batman operates in a Crapsack World in order to better perfect it as his old home. Sure, we might put on airs to help save the world, but Batman is going out and making a truly depressing world better, and his Tragic Dream is something many admire.
Batman's Rogues Gallery as a reflection of the heroBatman is generally considered to have one of the best, if not THE best, Rogues Gallery in comic books. This Troper posits that part of the success of Batman, and part of the contribution to his legendary status, is that his Rogue's Gallery is such a perfect shattered reflection of Batman himself.
Batman as Philosophical CritiqueThe entire comic series can be interpreted as a representation of the failure of conventional morality from a quasi-Nietzchean perspective. Philosophically speaking, Gotham City is a representation of everything that could possibly go wrong in a modern urban landscape. The system has broken down to a nightmarish degree. Corruption is rampant at every level of government. Street crime and urban blight are so prevalent that they're just considered part of everyday life. Even the most outwardly decent individual is just one traumatic experience from transforming into a baroque Serial Killer. The conventional forces for Law and order consistently fail to address the problems of the society they were created to serve, which necessitates the appearance of a non-conventional force (ie. a vigilante who makes extensive use of psychological warfare and theatrics, rather than logic and procedure). Modern society's problems have grown too large and too complex for its traditional ethics to address. Something new must be created to deal with these problems. Which brings us to The Joker. He is the extreme of criminal behavior that law is unable to resolve. A constant throughout the series is that Joker can not be redeemed. His madness cannot be treated or cured. In fact his madness is slightly contagious; trying to analyze him, or in some cases just spending a significant amount of time in his proximity, may drive you mad as well. He can't be contained either; imprison him and he'll just break out again. Only one thing can really be done with him...and no representative of law and order - not even Gotham's extraordinary agent of it - is willing or able to do that. Thou Shalt Not Kill is the one rule that no one will break, even though it will quite handily solve the unsolvable problem of the Joker, and that is presented to us as a good thing. Unfortunately traditional concepts of "good" and "evil" do not apply in a place like Gotham. The city has been abandoned by God, and the only reason God's laws hold any sway at all is because it gives them comfort to the citizens of the city to believe that they do. The Joker's continued existence - and the continued reign of terror he engages in - is the inevitable end product of the moral myopia/moral hypocrisy of Gotham City. Everyone in Gotham - including the vigilante who is technically outside the system - is applying a system of morality to a situation where it is no longer relevant, and in the process contributing to their own self-destruction.