Originally By: Dolly Parton It's forgivable to not even be aware that this is a cover, but Whitney's biggest hit song was indeed, not hers. It originally started life as a modest country ditty by the legendary Dolly Parton, just through a change in delivery and genre, Whitney changed the tone entirely. Whilst Dolly's original sounds like a farewell to a past love, Whitney's power ballad approach made it sound more like an undying declaration of love. Parton's version was highly minimalistic and reserved, Houston's was large and robust. This was the lead single from the soundtrack of The Bodyguard which would go on to become the best-selling soundtrack album ever and the song has almost been claimed by Whitney. In fact, this might possibly be the most successful cover in history.