Cover versions that are better than the original are many, here's a few for you:
Devo's Satisfaction
Blancmange's The Day Before You Came
Laibach's Life is Life
Pet Shop Boy's Always on my Mind
Bill Frisell's I Heard It Through The Grapevine
David Bowie's Sorrow
Any cover of a Bob Dylan song.
Devo's Satisfaction is the greatest example of this phenomenon.