The song was written by two english singer/songwriters named Anthony Newly and Leslie Bricusse. Its original purpose was for the 1965 musical "The Roar of the Greaseplant - The Smell of the Crowd", and was originally sung by Cy Grant.
I believe that Nina Simone's slightly contrasting version added a new light to the song and opened up many more doors for the growth of the song. Many different versions have been recorded since.
Versions and other songs containing samples of Nina Simone's version
The George Michael version contains samples, and is featured in Swedish hip hop group Fjärde Världen's song "Ingen Annan".
Simone's version was remixed by Joe Claussell in 2002 for the first volume of the Verve Remixed series.
The track "About You" on Mary J. Blige's album The Breakthrough features an unusual take on the song. The bulk of the recording consists of new lyrics, composed by Mary J. Blige, will.i.am and Keith Harris. However, the chorus samples several lines from "Feeling Good" as performed by Nina Simone. The original vocals are distorted so that the voice is almost unrecognizable. For this reason, Simone receives a credit as a feature artist, and writers Anthony Newley and Leslie Bricusse receive credit as writers. The track is produced by will.i.am. A song by 50 Cent Bad News contains a sample from the Nina Simone's version as well, as does Lil Wayne's "Birds Flying High." The song is also sampled in the song "New Day" from the debut collaborative studio album by American rappers Jay-Z and Kanye West Watch the Throne, released August 8, 2011. The song is also sampled in the song "How I feel" by Wax Tailor, on the album Tales of the Forgotten Melodies.
In April, 2011, PBS used the song to promote their airing of the remake of "Upstairs, Downstairs".
The vocal from the Nina Simone recording is also sampled in numerous house and dubstep tracks. Like by Huff & Herb or in Viper's - The Twister together with the Duran Duran sample.