Still her signature songs SUBG and BOY weren't no.1s. It's true that Stronger was her biggest song commercially but it's not necessary for a song to be no.1 to be a hit. I want a big memorable songs that will be happy Top10s than a rather forgettable song going to no.1 but no one will remember it in a half a year.
I would actually prefer an interview than a performance on Leno. She can win people over with her personality just as much as her music. Everyone knows she can sing flawlessly.