I think that female artists are criticized more than males because women often use their bodies and their sex appeal to get into the headlines, but male artists generally don’t. (Except maybe for usher who just can’t seem to keep his shirt on) When people criticize Christina Aguilera, it’s not because of her obvious talent, it’s because she presents herself as whore. (eg. ‘Dirrty’) People criticize her image, not her talent. Britney Spears is the same thing. People criticize her image and her choices much more than her voice. She has a good voice, although it is not nearly as strong as other good singers.
Women are criticized more in the media because they emphasize their bodies and sexuality, rather than their music. If they didn’t dress like prostitutes and make raunchy videos, we wouldn’t criticize them nearly as much. That’s why great artists like Cheryl Crow, Michelle Branch, Shakira and Alanis Morissette are not criticized nearly as much as female artists that use sex to sell records.
Artists like Christina and Britney are criticized because they set themselves up for it. If they weren’t so publicly trampy, they wouldn’t be so closely scrutinized.