I saw this video about a year ago and from time to time it comes up.  Here is a video demonstrating how many songs can be play with the same chord progression.

Facebook- The Axis Of Awesome

The Axis of Awesome is a comedy band from Australia that has made headlines in their home country along with the UK, Sweden and currently the United States.  They take jabs at pop songs as well as performing their own comedy songs.  This particular one demonstrates how many songs have the same chord progression and why some songs do really sound alike.  I got a kick out of it and hope you do as well.  Who do you think does the best job?  I'm going with Benny, guys like us have to stick together.  Enjoy!