As a Christian, does reading comics and following superheroes a form of Idolatry?Idolatry? No; I am a Christian, but I don't worship the superheroes.
That said, I do think you should exercise some care with the images and fantasies you fill your head with. Dark or violent images or worse, paranoid clichés, are things I prefer to avoid, mostly because I don't want to decorate my mind with such things. The omnipresence of paranoid and conspiratorial clichés in popular culture --
--all our government institutions are corrupt, faceless bureaucracies scheming to oppress us, all our business institutions are corrupt and recklessly greedy, and Our Hero is a violent loner who knows too much and who either remarkably walks away unscathed from his killing spree, or dies in a blaze of glory, for this is the only way to live free or do good in such a world --
-- these tropes are medical symptoms of a sin-sick nation. I am weary beyond the power of words to tell of seeing them endlessly repeated in American popular culture. I think you choose wisely to avoid them.
And this is why I still like the classic superheroes. They were created at a time when American popular culture was not so dominated by this narrative. If presented authentically they are symbols of hope, not a part of a bleak or dark world.