The Greatest Song of All Time

As I write this, the Grammy Awards are on, so I started thinking about my favorite music, and most specifically, my favorite song.  I have a lot of favorites, but the one that stands above the rest is without a doubt "Yesterday" by the Beatles.

The Guinness Book of World Records claims that it has the most cover versions of any song ever written with over 3,000 recorded renditions. In addition to the original Paul McCartney tune, there have been versions by Ray Charles, Frank Sinatra, Boyz II Men, Willie Nelson, Elvis Presley, LeeAnn Rimes, and many, many others.  The original is still the best. Its lyrics and melody really made an impression on me during a depressing time in my life. 

What do you all think of it?  And are there any other songs that can rank alongside it as the "greatest song of all time"?