The beatle's are another band who's music really isn't that exciting, but they were revolutionary in their time. U2's style has faded out of the mainstream these days, but in their prime they were one of those super groups who had no problem selling out stadiums anywhere in the world. Even if you dislike U2's sound, even if you hate them, you've got to acknowledge their legacy.
Also I do enjoy the 1980's early 1990's material.