Bill Haley indeed was a couple or three years ahead of Elvis. His sole genre (at least hitwise) was Rock-a-Billy cross-over from R&B. And he twice hit with the teen anthem of the 1950s, Rock Around The Clock (also used for awhile as the theme to Happy Days tv show.) Elvis, on the other hand was the was a complete package...rock, ballads, gospel with hits in each of those musics.