Ain't Nothing Like the Real Thing is a song by Marvin Gaye and Tammi Terrell from 1968. The lyrics describe looking at a picture and reading a letter and that these things, while comforting, are no substitute for looking upon someone in real life or hearing their voice speaking the words, hence the title of the song.
The idea expressed in the song was so strong that it was not long until it was co-opted by commercialism. Coca-Cola and Burger King came up with jingles and promotions suggesting their brands were the “real thing” so why would you settle for anything else.