I Heard It Through the Grapevine — Marvin Gaye (1968)

Motown's best-selling single to that date, this 1968 masterpiece spent 7 weeks at No. 1 on the Billboard Hot 100 and 8 weeks on the R&B chart. Marvin Gaye's version, released after Smokey Robinson and Gladys Knight's recordings, became one of the most covered songs of the era—The Rolling Stones used it on their 1969 tour, and Creedence Clearwater Revival's 11-minute 1970 cover introduced it to rock audiences. Compared to the typical Motown single, its cultural reach is unmatched; it outperforms #7's 1-week chart-topping run by 600% in longevity on the Hot 100.