I think that's slightly unfair. There are tons of interesting indie comics that are farther from the superhero genre than Invincible.(East of West/The Wicked and the Divine are the ones that most readily spring to mind). They certainly at least share some DNA with superhero books, but variety exists

I love the Walt+ Weezie tree graffitti

There's definitely an Avengers story(I think under Busiek?) that has Kulan Gath create a similar boundary that transforms anyone who crosses it. I can't remember if he transforms a city or just creates one though.

I think this issue might have the most commonly posted Cap panel I've seen on the internet(besides maybe the Strazinzki "You move" one. It's really something interesting.