Hollywood is a male-centered business. Once you think that statement over, it is.
There are almost never any good female roles. Actresses are usually cast to play a whiny bitch (*cough* Annette Bening in American Beauty *cough*) or to flash some flesh. It's ridiculous.
Strong female roles started to dwindle by the end of the 70's, around the same time the feminist movement started to end. Ironic? Probably.
If there are good female roles in a movie, there's a good chance they're in the supporting role rather than the lead.
Performances are one thing. Female directors and writers are another matter. There have only four female directors nominated at the Oscars (with one winning).
Most female directors tend to work on movies aimed at women. Or, as they're better known as, romantic comedies. A few managed to veer away from the stereotype (ie, Kathryn Bigelow, Sofia Coppola), but a number of them still direct/write romantic comedies.
Have you noticed when you see a "top performances of the year" list, the majority of it is male performances? Try to remember that when you read one.
A few male directors have strong female performances as a theme throughout their movies (ie, Billy Wilder, Alfred Hitchcock, Ridley Scott), which is good. But now, that theme has dwindled down as much as the strong female role itself.
Why is that? Why are the best parts written for men? Why are the best roles for women tend to be in the supporting rank?