I am going to name the Top 10 for the 5 year period of 2011-2015

Why? I personally think that we should judge the Top 10 based off a given time period because it changes yearly. For example, Adele is very successful right now but once she is done with this album and takes a break in between she won't be on any lists despite possibly owning again in 2013/2014.
Again, my prediction for the Top 10 females who will have the most success during 2011-2015

(Not counting any new Artists of the future...in order)
#1__Kelly Clarkson
#2__Adele
#3__Lady Gaga
#4__Katy Perry
#5__Rihanna
#6__Avril Lavigne
#7__Pink
#8__Mariah Carey
#9__Christina Aguilera
#10__Britney Spears