I'm a woman and always hated the "It's pink and there are unicorns on it! It MUST be for YOU!" But I was what they called a tomboy and preferred robots to ponies. The thing is, most women I know these days... which is not all women of course, so take that with a grain of salt... never felt that kind of marketing appealed to them. Or at least the most extreme variants of that marketing (everything that's just sparkly and pink and substanceless).
I think it's a case of, honestly, marketers not knowing how to market to girls. Things I've read show that a given version of these products (save Barbie and the EZ Bake oven) don't last long or sell well... sure a clone will pop up a year later, but it won't do well either. There IS a certain subset of girls that WILL go for the Pink Pony Princess thing and they know they can capture that audience, but the rest of the girls will continue to say WTF (along with a majority of boys) and won't get anything marketed to them.
Based on what I've read and my own experience, girls generally enjoy creative play, role play ("Let's play house"), and cooperative play (we prefer to follow our competitive instincts when we reach the age of 12 and torture each other socially instead). Things that attract most girls won't therefore be something specifically labelled "for girls" but simply be things that girls can explore their creativity with.... art supplies (and things like LEGO) and board games that tend to be marketed as "family games" rather than specifically "for girls."
The girly stuff that IS successful, like Barbie and EZ Bake, are because they fill these niches, whether they're pink or not. EZ Bake you can play pretend with while also producing real food and share it; no surprise why that's appealing. Barbie filled a much needed niche in the role play world.... baby dolls are fun to pretend they're babies, but once you get old enough to get sick of that, they become less interesting and it's hard to imagine them as anything else. Dollhouse dolls are more easily manipulable to create stories with (something girls stereotypically love to do) but they're usually too small to re-dress or fit in your hand comfortably. Barbie is a good size and has a lot of clothes so you can dress her to fill the role you want to imagine her in that day, more than just the "pink stuff."
I liked my Barbies but they seldom wore pink or rode ponies; they wore darker, trendier clothes, and when I became interested in fantasy and sci fi, they started getting cloaks, homemade armor, and cocktail swords for weapons, and rode Voltron lions for locomotion. (What sucked is I had to get my own swords and armor, but the way the toys were made made it easy to do.) The interesting thing is I had action figures--being a child of the 80s, He-Man and She-Ra figures plus some Transformers and the aforementioned Voltron--but I preferred to send Barbie off to fight evil over She-Ra because again, she was bigger without being too big, and easier to physically manipulate. (Barbie also put Voltron to work in her kitchen, but that's a story for another day.)
So, I would say that's why that in particular does well and doesn't always suck (at least of course, in my few).
As an aside: Mattel makes licensed Superhero Barbies: here's Black Canary, who looks pretty awesome: http://www.barbiecollector.com/shop/product.aspx?sku=L9640
They clearly know there are people who will want to buy non-pink, frilly Barbie dolls. The interesting thing is, though, these are in the more expensive "collector" set--largely meant for adult women, not girls. Something interesting to think about. ('Specially since my younger niece LOVES superheroes... hmm.)
Other "toys for girls" I don't think suck:
American Girl Dolls: I don't see these having crossover appeal to boys, but they're not frilly pink princesses, they are well-designed, and they each come with a historical story that educates about the time period they come from without being heavy handed. They're girls toys--POPULAR girls' toys if my nieces' enthusiasm for them is any indication--which teach something far more than "dress pretty and be snooty."
Well, and that's all currently. That's the sad part. (By the way, if you missed it, yes I agree most "toys for girls" suck.)
From my childhood, we had Jem dolls. The main character did have a lot of pink to her (along with "glamour, glitter, fashion, and fame"), but they were adventuring rock stars with brightly colored 80s hair. Some of their clothes were actually pretty punk. I will venture to say they were pretty kickass despite the pink and the glitter, and apparently Jem had quite a male following, if not of the dolls then at least of the accompanying cartoon series. It's a rare example of a girl toy/cartoon line that attracted boys----at least enough that Jem's cartoon voice actress (for the speaking part, oddly enough) recently made a music video dedicated to her male fans: http://www.youtube.com/watch?v=MK3WAQWLLsc
This teal dear brought to you by DeathQuaker.