Lady GaGa = She "dissapeared" months ago with "Marry The Flop"
Beyonce = Had no success with "4" (General, not only Urban and those stuff)
Katy Perry =she had huge "era" and people still buy her things, so no overexpousall for her.
Britney = Had a good year, already said she was taking a break
Adele = Just appeared last year and it's having huges amounts of success.
Madonna = Reappeared this 3 months ago.
Christina = Well, the last thing she did in 3/4 years was "move's Like Jagger" feature. Overexposed?
My choice is Nicki Minaj. She had like 20 million singles released.
And Rihanna is obviously missing