If you think a lot of pop music sounds the same you may not be crazy. Let the Axis of Awesome demonstrate the power of the prototypical 4 chord song.
Not convinced? Here's a video of 65 snippets of 4 chord songs by the original artists with the speed and pitch matched into one continuous medley.
But don't think it just started with modern pop songs. Songs have sounded alike for a long time. Don't believe me? Listen to the Pachelbel Rant by Rob Paravonian. Sound familiar?
Now you know why I can't listen to top 40 anymore.