Based on the iconic (or lack thereof) nature of all careers' listed, Xtina's voice alone trumps the other talents.
Based on stats the same applies -
This is the list of females of the year according to the Billboard year end charts since 1997 (year by year):
1997: LeAnn Rimes
1998: Shania Twain
1999: Britney Spears
2000: Christina Aguilera
2001: Jennifer Lopez
2002: Ashanti
2003: Christina Aguilera
2004: Alicia Keys
2005: Kelly Clarkson
2006: Rihanna
2007: Fergie
2008: Rihanna
2009: Taylor Swift
2010: Lady Gaga
Some of these gals can't even impact the charts, yet they're supposed to impact the industry in great lengths? If Xtina can own 2 years, why couldn't Britney do it twice? Why couldn't Beyonce do it at all?
NOW THAT"S IMPACT!