I can't bring myself to name just one band as my ultimate favorite. I can mention a few bands that have only rarely put out music that I don't love, though. But, since
no band can be perfect all the time, I can't really fault them for an occasional sub-par song or
three, especially if their catalog stretches beyond 10 or 15 years.
Anyway, here's my short list of bands fitting that description:
NOFX, Led Zeppelin, Cake, Red Hot Chili Peppers, A Tribe Called Quest, The Doors
I can also
throw together a short list of bands that come close, but whose quality dropped off too much later in their careers:
The Cure: I'm a huge fan of all their music up to and including the
Disintegration album.
Pink Floyd: Love, love, love all their albums up to and including
The Wall.
Electric Light Orchestra: Their albums up to and including
Out of the Blue are all nearly perfect.
And then I suppose there are some "honorable mention" bands who always seem to put out great music, but slip up a bit too frequently to get top honors:
KMFDM, Queens of the Stone Age, Foo Fighters, System of a Down
I guess that's about it, off the top of my head.