I agree that generalities are a "quick and easy" way of looking at the world- and should be avoided, but I think I'm looking at it more as "young girls vs. young boys - not differences in adult sexes, per se.

As a father of two 3 year old boys, I can say that the clothing or toys section in a store for girls is very distinctly different from boys. You can buy jeans for girls but the selection is not as vast. Young kids are exposed to that "segregation" at a young age. It doesn't mean girls can't play with toy dump trucks, but the social forces at work here are different, I think. Kids are more easily influenced by their environment.

I worked at a place that put on stage shows for kids, and the one season was not as succesful because there weren't enough "girl's" shows. It sounds silly, but it seemed to be true. Dora The Explorer is more popular for girls than for boys; the converse being true with Bob The Builder.
The Hulk can appeal to anyone really, especially because it isn't a one dimensional kind of show. For me, I think young kids follow social norms differently than adults. One shouldn't assume anything about anyone but I have a hard time imagining a young girl buying , say, a Hulk comic book.