Well, to avoid the nonsense of the Plant thread, I'm sticking to MY FAVORITES here:
Sabbath and Zeppelin top the list.
Maiden, Aerosmith, Marillion, MSG, Queen and Kiss are not far behind.
I'd throw out for consideration:
The Cars
U2
Night Ranger (Dawn Patrol, Midnight Madness, 7 Wishes, Big Life)
Cheap Trick (CT, In Color, Heaven Tonight, Dream Police; add "The Flame" and that's essentially every CT greatest hits ever put out)
ELP (ELP, Pictures, Tarkus, Trilogy)