Hey if it wasnt for Elvis, there wouldnt be Chuck Berry
If it wasnt for Chuck Berry, there wouldnt be The Beatles
If it wasnt for The Beatles, there wouldnt be Rolling Stones, Cream
If it wasnt for Cream, there wouldnt be Led Zepplin
If it wasnt for the Rolling Stones, there wouldnt be The Who
If it wasnt for the Who, there wouldnt be Jimi Hendrix
If it wasnt for Jimi Hendrix, there wouldnt Deep Purple, Black Sabbath
If it wasnt for Black Sabbath, there wouldnt be AC/DC
If it wasnt for ACDC, there wouldnt be Nirvana, Metallica
If it wasnt for Nirvana, there wouldnt be Green Day, Silverchair
If it wasnt for Green Day, there wouldnt be Living End
If it wasnt for Living End, AC/DC, Green Day, there wouldnt be Jet
I'm not saying most of these bands copied other bands' riffs or music, but they influenced other bands. The music changed in every era, Elvis started the change of not only Rock 'n' Roll, but also music. And so did other bands as the years went by.