It's a damned hard question, really.
In the 60's, you had: The Beatles, The Rolling Stones, Cream, Bob Dylan, CCR, The Kinks, The Small Faces, Hendrix, The Who, Jefferson Airplane etc.
In the 70's, you had: Joy Division, Queen, Bay City Rollers, David Bowie, Led Zeppelin, Supertramp, 10CC, Status Quo, Jethro Tull, The Sweet, Nick Drake, Electric Light Orchestra, Black Sabbath, and some of the old bands from the 60's kind of evolved into being "70s" as well.
In the 80's, you had: Michael Jackson, The Jam, Ultravox, New Order, Spandau Ballet, Echo and the Bunnymen, Toto, and plenty more, as well as the usual phenomenon of older bands catching up with the times.
The 90's was a bit sucky, same as now.
It all depends on what sort of music you like - I've listed some of my own favourites.