Gaines literally created the first four-color side stitched newsprint pamphlet for Dell Publishing in the early 1930s, thus inventing the format still used to this day.
He is also credited with creating the superhero genre through bringing in Superman when he was publisher of DC Comics. He also created All American, the first all-superhero line of comics, with Green Lantern, The Flash, and the Justice Society of America, and directly inspired the creation of Wonder Woman.
Gaines was also publisher of Educational Comics, which concentrated on Bible Stories and funny animals. Gaines left Educational Comics to his son, William Gaines, who turned it into Entertaining Comics and later created MAD Magazine.