Gladys Knight and The Pips weren't the first people to record this song, but they were the first to release it. Their release was soon eclipsed by Marvin Gaye's recording (actually completed before the Knight recording), but both versions have inspired a lot of love... and a lot of covers. Here are some of the best.
Bobby Taylor & The Vancouvers (who toured with Gladys & The Pips) do a cover, and then The Rustix (the first white band signed to Motown) does a cover. Then Creedence Clearwater Revival present their extended, eleven-minute workout of the song. (There also exist dueling live versions I haven't included here -- to keep it under ten versions -- from John Fogerty and from Creedence Clearwater Revisited, the band with the other two surviving members in it.)
We have a bluegrass cover (from the best ripoff bargain-bin album I ever bought, Pickin' on Creedence Clearwater Revival), and then Barrett Strong, the song's co-writer, tells us what it was like to write songs at Motown, and sings a great, stripped-down version.
Finally, we close with a remix of the Pips' version.