I'm a guy, and watch Naruto. I thinks it's a good anime, lots a fun, and a great story. But yeah, seems like more girls at least from the NDK forums, watch it. To be honest it seems like a lot of girls who watch it simply watch to go gaga or Sasuke and Naruto. But then, that's not saying ALL fan girls of the show are that way.
For me, I like the story of Naruto and how expansive it is. While yeah, there's a main plot, at the same time there're so many branches that make people want to learn more about this village, these characters, etc. I really like that about Naruto, it's kinda rare for an anime to do that. Not saying they're bad, just that most animes are not nearly as long so it makes sense. And some just don't have the type of story that is open for an expansive world. Again, not a bad thing.
But Naruto on the other hand really can make you enjoy the show outside the main plot. Like the seasons of "filler episodes". Now a lot of people gripe about them, my friend included, but I enjoy them for the chance to see more action from the characters other than Naruto and Sakura and Sasuke ya know. I guess that's what really gets me into the show, though the action if fun to.