Marvel changed the face of superheroes pretty much from the beginning, way back when in the Golden Age. However, they truly highlighted superheroes' potential starting with the Silver Age. Those early '60s debuts created legends like few others. That said, not all of them were perfect right off the bat. Some of them took time to get to where they are.
Source：https://www.cbr.com/marvel-heroes-perfect-comic-debut/
