Realism is sort of a hot-button word around here. When most people on here say realism I think what they actually mean is plausibility. There is also a difference between physical plausibility and character actions/motivations/emotions that are plausible. But at the end of the day it's all a balancing act like on one of those old fashioned scales
On one side you have the fantastic stuff which must be present in some form to even qualify as a superhero film; on the other is the mundane stuff that keeps it all grounded. I'm of the belief that you can have as much fantastic stuff as you want provided that your mundane aspects are of at least equal weight in terms of story/characters/mythos/etc. It's a film maker's job to figure out how to keep it all balanced.