You are right. I thought she was at her best in the '89 - '91 era, but she hit a stinker with 'Erotica' in 1992 and it was one of her lowest selling albums, she rebounded, but tanked later with 'American Life' in 2003. Her highest selling album was 'True Blue' w/ 24,000,000 copies. I think Lady Gaga is already at 10,000,000 - 12,000,000 after a couple of years.... We'll see what happens.
FTR, I like both. Madonna has said nothing but good things about Lady Gaga and vice-versa. If they don't care about competing w/ one another, why should we?
Hats off to Madonna, but quite a few of her songs were as well.
BTW, 'Born this Way' is squashing Britney Spears 'Hold it Against Me' in its first week of sales, and it is looking to debut at No. 1 on the Billboard Hot 100: