You ask "why there hasn't been a "lady equivalent" to Transformers or G.I. Joe on the big screen as of yet", but don't you think that Harry Potter, and The Golden Compass are examples of female geekdom? Not to mention Twilight... I mean, I know boys do read them too, but at my school, they were definately more of a girl thing.
Although I loved My Little Pony and Sylvanian Families as a child, I have no desire to see them on the big screen... when girls grow up, they replace these "cute characters" with REAL cuteness; ie, pets or babies. And boys replace toy robots with real cars or motorbikes or video game simulations
p.s: every other example on your list made me feel ill and embarrassed to be a woman. The characters in that 'Sailor Moon' especially makes me want to vomit or kick something.