10 Best Comic Book Universes
3. DC Universe
The DC Universe began with the publishing of All Star Comics #3 in 1939, and has remained the longest-running comic book universe in history. The Golden Age of Comics was defined by many of DC's titles, which included Superman, Batman, Detective Comics, Green Lantern, Wonder Woman, and many more.
Over the years, the DC Universe expanded to include parallel realities dubbed "Earths," but given a number such as Earth-2. As this expanded into the Bronze Age, characters became convoluted and confusing. Multiple origin stories and expansive power levels made some like Superman into gods.
To sort it all out, DC launched the Crisis on Infinite Earths crossover event, which served to wipe out most of the parallel realities and return the DC Universe to a sense of relative continuity. Every few years, DC likes to shake the universe up a little with similar crossover events to keep the fans on their toes.
The DC Universe is incredibly expansive, and each character has their own particular reality, but still manages to interact with others. This helped lead to the creation of the Justice Society of America and its successor, the Justice League of America. Crossovers and the DC Multiverse work well enough that you can consider the DC Multiverse as one incredible universe full of different possibilities.