According to the definition of that word (one of many),
"legend - person who inspires or achieves legendary fame"
it's clear that being a legend is all about the fame. We can say Madonna is a legend, because she's the most famous
female pop singer. We can say Brtiney Spears is a legend also, cause she's 2nd after Madonna most famous female.
Now if we think about it - who's the most famous female singer
right now?
It's Rihanna.