Ok, there's this guy on the internet, DJ Earworm, who makes amazing mashups of songs, and here's his 2009 Mashup.
It's a mashup of the top 25 songs of 2009 and it's great! It's called United State of Pop 2009 (Blame It On The Pop). Click on the link and listen!
United State of Pop 2009
Your Music Lover,