The Beatles. Period. Even if you don't like them, you still need to acknowledge the fact that they have had more influence over the music industry than any other band or act ever. Disagree? Think about this. The Beatles brought albums to the forefront of the music scene. Before them artists just released singles and sometimes albums with a bunch of filler tracks, usually covers. The Beatles actually wrote entire albums, becoming the base for just about EVERY BAND today. Not only that, but they have sold more albums than anyother act, have had dozens of hits, have several albums in the Rolling Stone's Top 500 Albums list, are #1 in their Best Band list, and have has dozens of hits. If you think you dislike them, I garentee you have heard a few songs you like that you don't know are by them.
The Beatles are the best band ever.