We're talking about it now, but as far as I can see you intentionally left out the other major - and ultimately bigger - breakout act of 2008. You didn't have to choose only one.
To be fair, Just Dance didn't hit #1 until January 2009. Within 2008, Katy's breakthrough was much bigger.
Plus, is it really trolling to say you think one artist is more popular than another artist?
the exposer 
... "vagina" is not censored, but the short version of it, is? 
I thought it was the "P" word that is a synonym of Cat. 