Worst ever: Led Zeppelin. Terrible live, and (except John-Paul Jones), not very good musicians.
Followed by the most overrated and/or not very good (in no order):
U2, Nirvana, Metallica, most current "rock" bands (a la My Chemical Romance, AFI, and so on), most 60's bands (a la Grateful Dead, The Doors, The Youngbloods, and the like), most 80's metal, all Christian rock, late Genesis (Phil Collins-era), most pop-rock (a la Bruce Hornsby, Cutting Crew and others of that ilk), most punk, girl-pop (Britney, Brandy, Jessica/Ashlee Simpson, Avril, and so on), the vast majority of latter-day rap, and late country, the list is practically endless.
Good stuff (in no order): a lot of new-wave, some no-wave, Industrial (mostly early), some Ambient (Eno, et cetera), Noise, Chrome, Last Exit, BeBop, Progressive Rock (Yes, King Crimson, early Genesis, Rush, and so on), Classical, Pink Floyd, NoMeansNo, David Bowie, most 70's pop, James Taylor, a lot of World Music, Peter Gabriel, Carol King, Neil Diamond, Sonny Sharrock, Ronald Shannon-Jackson, James Blood Ulmer, Paul Simon, CoC, Chiaroscuro, JohnColtrane, Mahavishnu, good soundtracks (Morricone, Glass, and others), Naked City, John Zorn, Kazumi Watanabe, Bruford, Japan, The Beatles, The Rolling Stones, and on and on...
Later kids!
--JB