It's pretty common to hear people to claim that Batman, Superman and Spiderman are the most popular superheroes. However, with the probable exception of Batman, lately, due to movies and other factors, it seems like other superheroes may be surpassing them in terms of popularity.
Have there been any legitimate studies on who the most popular superheroes are in different parts of the world? If so, what were their results? I would define popularity and terms of how well-known and liked they are.