Always late to a discussion, but here goes...
The transition from Madonna to Britney to Lady Gaga makes the most sense, and that timeline shows a shift in both the pop climate and how the mainstream views female empowerment. Madonna earned her success (and her many failures) through a cut-throat, neo-feminist mentality. She demanded respect with a personality and political edge that most in hindsight would call confrontational and even crude. Her brand of feminism was powerful and attention-grabbing, but it was also flimsy and short-lived. You can prove that that mentality was short-lived because of her endless re-inventions. Yes, many of her re-inventions followed an era of success (which showed her giant lady balls), but the fact is that she re-invented her image and music because she NEEDED to.
I'm not trying to diminish her legacy or her ability to keep the spotlight on her, because she has. But it's obvious from looking at the mainstream opinion of her as a WOMAN that she's garnered slightly more disdain and hatred than pure, unadulterated love. It was her intention from the onset, but it reflects how her brand of raw, in-your-face controversy was no longer wanted or needed by people by the start of the 2000s. Speaking only about the music, I think that experimental and risk-taking spirit in releasing different kinds of albums became very unpopular by the late 90s, and there was a transition into more of a dedicated FORMULA with pop acts. Music studios retained their control both on the business and the creative side, and hence Britney Spears was born.
Britney's legacy represents the fetishizing of women in a way reminiscent of the 1960s pin-up days . When she debuted in that school-girl dress and pig tails it was obvious that the world was ready (again) for a young, innocent woman to inspire people. On the business side, it reflected a tightening of creative direction, song writers re-emerged with power and responsibility. It was during this pop era that things took a creative stall, but nobody can deny that Britney's legacy is that of fully realized, traditionally PERFECT pop music. Manufactured, unoriginal, yes. But quantifiably perfect. She inspired a cavalcade of pop acts that were front-loaded with one or two good pop songs, but their quick descent into obscurity showed that labels put more credence in looks than creative talent. I think her meltdown showed fragility in more ways than just her personal life. People were ready for a bold, powerful woman to take pop by the balls and inspire people in a new, better way.
Lady Gaga is the anti-Britney. But she's also the anti-Madonna. She counters Britney's fragility and quiet emphasis on creative direction with boldness and an almost pretentious insistence of talking up her own creativity. She counters Madonna's crassness and rude rebellion with an intelligent articulation that made her brand of rebellion more intellectual and believable. Her brand of music isn't quite as realized as her political/personality brand, but it's getting there. She's energized the pop scene in a more authentic way than Britney did; in both bold style and politically-charged music. As a fan of both Britney and Madonna, she's obviously studied up. Her style of unpredictability is more fast-changing and schizophrenic than Madonna's, but (at least so far) it doesn't stem from a need to regain attention so much as a testament to her craving experimentation and testing mainstream tolerance. She's meta in a way Madonna didn't understand until later in her career, and even then couldn't quite get a handle of it. In her short career she's gained respect from industry godfathers and other mainstream mediums in ways Madonna always failed to do. If Gaga's legacy plays out the way she wants it to, then she'll be remembered as the all-time quintessential pop star.
Thanks for another beautiful Rumination on Pop, Sis.