I see no need just focusing on american superhero stuff, there's so much more out there. But I guess that's what flies here.
Really, there are a lot of more easy stuff to start with elsewhere, selfcontained books and such. I usually find more pleasure in the books that end with "The End", rather than "To be continued...", but that's just my preferences.
As a kid I never even saw a superhero comic, and really got started with Tintin (I'm delightfully european), though I had read a lot of stuff before that. I generally find the French-Belgian stuff great starting points for comic readers, especially young ones. The visuals are not too complicated, but they still have depth, and the stories aren't braindead violent crap.
The thing is that comics are a medium like any other. It's a little hard to know what works for you, and what doesn't, when it's such a broad subject. Just like literature, movies, music, games, etc.
I also saw some people above disregarding manga, because somehow those are not comics. (?)
Fascinating stuff.