There are many factors as to why it's popular, such as creativity, picture, depth of storyline, etc... i'm sure many of us here loved our batman, superman, x-men cartoons when we were little 🙂. Though if compared to some anime like Naruto and Bleach, it's just far better. Hence the reason why it's popular and why tv stations in US are airing anime. Look at how big Pokemon became...
Also, theres this one guy that goes to the same college as me. He shows up everyday wearing a Konoha headband (Naruto's village symbol) and everytime I goto the computer lab to print my essay, I see HIM on the computer. Think you know what he's doing? you guessed it... watching Naruto :roll: