system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are Marvel comics based in real world locations and DC comics based in fictional ones based on real world locations?
gpt
DC started the tradition in 1938 with Superman and Metropolis. Superman was originally going to be a newspaper strip, and there was concern that if they set it in a specific city (Cleveland was their first attempt), it wouldn't sell as well elsewhere. From there, the tradition that DC Superheroes had fictional cities arose, like Batman having Gotham. Superman set a standard, and everyone tried copying what his series established.

In 1961, Stan Lee made the idea that he'd do his own take on Superheroes, and having them be set in New York would not only allow all the heroes and villains to interact with each other, but would stand out in comparison to DC and make it seem more "real" because you have never seen the Daily Planet building, but you have seen the George Washington Bridge. 

Both companies have used the other tactic on occasion. Wonder Woman is traditionally based in real world cities, usually Washington DC or New York. Marvel invents locations like Genosha or Latveria or Wakanda. But in short, it's because Stan Lee wanted Marvel to make something different than how DC did. And it seemed to work.