“The stories told in Japanese manga and anime are incredibly powerful. I often find myself wondering, ‘What is missing in Western comics, and why aren’t they able to achieve the same flavor?’ Also, I think manga has an ‘advantage’ over American comics, which are mostly about superheroes, and that’s where the majority of sales and readers are concentrated.“
I think it mainly comes down to price and marketing. There is way more to comics than big two and superheroes in general. But they are only known to the comic enthusiasts, they very rarely manage to reach mainstream pop culture.
Manga is great at making itself known, either through anime or some other means. Most American comics don’t have the means for that and European comics probably don’t care very much.