I saw the phrase "Queen of Pop" in the thread title and waltzed in here wondering why on earth Ke$ha was being compared to Madonna... but now I see the error.
Anyways, since I'm here, I guess I'll share my thoughts on the initial question: I believe Gaga has achieved more than Ke$ha within the given timescale because all Ke$ha really has going for her are her singles. TiK ToK may have sold x amount of copies and other singles have been hits, but Gaga has yet to achieve a single that hasn't peaked below the top 10. And that's really where it stops with the comparisons - Gaga has her overall creativity on her side. Gaga had already shown artistic growth and exploration with her EP, whereas Ke$ha's EP was nothing different to Animal.
