I think she became a cultural icon in 1989/1990/1991 with Like a Prayer, MTV, Vogue, Blond Ambition, Justify My Love, The Immaculate Collection and Truth or Dare.

I think she became an actually respected music legend with Ray of Light, for two reasons - firstly, she made an acclaimed, mature and successful record without selling on sex or religious controversy and secondly, she survived the '80s AND the '90s, a feat for even the biggest of rock artists, never mind the far more fickle pop genre.

I think another thing that contributed was the fact that all the popstars appearing in the late '90s/early '00s were literally all based on her blueprints, but were all inferior to her.