Madonna. With Gaga it was what she's wearing a lot, recently it's gotten less fashion focused and her antics/persona really can't keep up with that! Madonna is/was all about her actions, clothing, music, and videos working together as a cohesive whole.
No Madonna = No Lady Gaga.
Madonna literally birthed her. And Madonna has Like A Prayer, most creative song and video by a female popstar, so why on earth would anyone pose such a question.