When most people think of a superhero, they think of a character published by DC Comics, such as Superman, Batman or Wonder Woman, or by Marvel Comics, publisher of Spider-Man, Captain America and Iron Man. Although there are a wide range of comic publishers, the "Big Two" have dominated comic stands for decades. Many creators have worked for both companies, and the two ranges have many similarities, but there are still important differences between them.
Of the Big Two, DC has the longest history in the superhero limelight. The first issue of Action Comics, published in 1938, introduced Superman. The first comic-book superhero was an instant hit, inspiring dozens of imitators. Although the company that would become Marvel was active in this period, it wasn't until 1961 that artist Jack Kirby and writer Stan Lee created the Fantastic Four, the first of a new breed of Marvel superheroes.
Heroes and Villains
In the 1960s, the difference between Marvel and DC characters was striking. DC's heroes tended to be iconic, with bold, recognizable imagery. DC stories focused on over-the-top adventure and heroic feats, while Marvel's stories were darker and more grounded. Spider-Man, created by Steve Ditko and Stan Lee, was outwardly a cocky crime-fighter, but under the mask was a flawed, anxious, guilt-wracked teenager. Other Marvel heroes were similarly tormented: the X-Men were shunned and hated by society, and the Thing saw his monstrous appearance as a terrible curse. DC did begin to adapt its stories to focus on more human elements, but they weren't always successful.
Powers and Abilities
Hand-in-hand with Marvel's focus on human problems came a slightly smaller scale in terms of heroes and their powers. Marvel characters were generally less powerful than their DC counterparts. For example, at the height of his powers, the Superman of the late 1950s and 1960s was vastly powerful, capable of moving planets in their orbits and battling whole armies. Even Batman, who technically lacked super-powers, commanded an arsenal of high-tech gadgets that put him on the same level as the aliens, immortals and other wonders he fought alongside. In contrast, as comics critic and writer Chris Sims described, the Marvel universe was "built on limitations."
New York and Metropolis
Although early Batman adventures took place in a real city -- "Gotham" is a traditional nickname for New York City -- DC characters tended to settle in fictional cities, from Superman's Metropolis to Green Arrow's Star City. By contrast, Marvel's characters lived in a New York created by writers and artists who were mostly longtime residents. Real events such as the moon landing were reflected in Marvel Comics. This tradition has continued into the modern day. For instance, whenever the President of the United States appears in Marvel comics, the current real-world president is used, while in DC comics the president is a fictional character. Fictional locations do exist in Marvel books, and some DC heroes are based in real cities, but in general the Marvel setting is more grounded in the real world.
DC Continuity and the Multiverse
As comic fans began to grow older, they showed an increasing concern for "continuity" -- that is, consistency between characters' different adventures. This was especially a problem for DC, which often had multiple versions of the same character. For instance, the Flash of the 1960s was a completely different character from the Flash of the 1940s. To reconcile this and other problems, DC's writers created the idea of a multiverse, a universe containing many different versions of our world, each with its own heroes and villains. When the multiverse became too confusing, DC simplified it with a special event, 1985's Crisis on Infinite Earths. Since then, DC has rebooted its continuity frequently, with the most recent reboot happening in 2011 with "The New 52."
Marvel Continuity and "Marvel Time"
Unlike DC, Marvel has yet to reboot its entire continuity as of 2014. Initially, Marvel characters aged in real time. Both Spider-Man and the Human Torch completed high school and started college during the early years of their comics. However, this caused problems -- the Human Torch can hardly be the young, hot-headed member of the Fantastic Four once he's middle-aged. To solve this problem, Marvel instituted "Marvel Time." Characters in the Marvel Universe age very slowly, with history being defined loosely -- an event might have happened "five years ago," for instance, rather than in a specific year. This approach still causes problems, particularly for characters who have ties to a specific historical event, like Vietnam war veteran the Punisher or Holocaust survivor Magneto. For the most part, however, Marvel's approach of simply not discussing the issue keeps stories flowing smoothly.
Two Sides of the Same Street
Although there are some notable differences, Marvel and DC are similar in many ways. Both are now subsidiaries of larger entertainment companies, Marvel owned by Disney and DC by Warner Brothers spinoff DC Entertainment. Historically, both companies have employed many of the same creators: Marvel icons such as Jack Kirby and Roy Thomas both also worked for DC, while DC comics co-publisher Jim Lee made his name at Marvel in the 1990s. Frank Miller's seminal work on Batman in the 1980s was prefigured by his work on Daredevil for Marvel. With so many creators working for both companies, it's no surprise that there are some similarities.