Unchained Melody was sung not by dozens of artists, but by Hundreds. It was a powerful melody often sung to best display the vocal climax of an artists singing talents. The first I remember was sung by (born blind) Al Hibbler in 1955. He was the second artist to record this song but his was the first hit version. The first known performance was by Todd Duncan, who sang it in the 1955 prison movie Unchained.
The Songwriters Hall of Fame says there have been more than 1,500 recordings by over 670 artists in multiple languages, so a literally complete list would be enormous. Still we’ve compiled a list of a good many, sixty of the identifiable recording artists a good many of which were released around its introduction in the mid fifties. We’ve highlighted the top 10 of all time with ⭐.
A special note on the The Righteous Brothers' recording of 1965. It didn't actually top the American charts but it peaked at No. 4. Bobby Hatfield's solo vocal became what the Songwriters Hall of Fame calls the “jukebox standard.” His alteration of the melody in the final verse became so influential that many later singers essentially covered Hatfield's version rather than the original 1955 arrangement. Then in 1990 the movie Ghost came along and gave that 25-year-old recording an extraordinary second life. It returned to number 1 in the Billboard top 40.
Lastly if you are wondering where Unchained Melody fits in the 'of all time recordings', it ranks number 3 behind Summertime from Porgy & Bess released 20 years earlier. And number 2, Yesterday by the Beatles 10 years later.