Well I haven't listened to Pop enough probably. The thing about U2 is they can make an album with one sound, like War, and another like Zooropa (this album is an acquired taste) and both kick ass. They really do have more than one sound and, unlike most groups, all their sounds are great.
Plus their last album is one of the best. They are totally not has-beens, which is great for a band of this age.