I think variation in theme plays a big part as well as the fact that Star Wars is more akin to cowboys and indians. Much easier for kids to get into.
I'm hoping that Abrams can give Star Wars more depth than it's had before in terms of a plot and quite frankly finding some actors who actually are good at their craft while not losing the child appeal that the series has had.
One thing I think JK Rowling did brilliantly with the Potter series is that she deepened and darkened the story without
IMO making it less appealing to children. In so doing it broadened the fan base.