Sometimes a cover song is the one that is the hit while the original was barely noticed. One example is the song "(They long to be) Close to You" which most people associate with The Carpenters.
The song was initially recorded by Richard Chamberlain(Dr. Kildaire) in 1963. It was also done by Dionne Warwick in the mid 60s. Burt Bacarach even recorded his own tune (he wrote the song) in 1968.
However, it wasn't until the Carpenters recorded it in 1970 that it broke through and dominated top 40 for a while and then became a mainstay of lite stations for many years to come.
Same deal with that song that Whitney Houston made popular "I IIIIIIIIIEIIIII will always love you" . The song was recorded years earlier by Dolly Parton.