That's a tough one...
The Brothers Gibb (Bee Gees) have had hits in the 60's, 70's, 80's and 90's, and have also written for other performers who made hits of their songs...
Micheal Jackson has had hits in the 80's and 90's...
Who's had the most hit songs that have "staying" power, (are still loved years later)?
My Bob Dylan impression: "Ah bleh bla dah ag he gla."
Kurt Cobain (RIP dude)