I think for me one think that elevates a good band to something even better is, the double album. Not just a crappy, cheap double 'live' album, a double studio album. At times you get these overlapping themes almost like a symphony.
My top five are::
The Beatles :: White Album
Pink Floyd :: The Wall
The Cure :: Kiss me, Kiss me, Kiss me
The Whitlams :: Little Cloud
Nick Cave :: Abattoir Blues/The Lyre of Orpheus
Its interesting U2 hasn't got there with a double though I think Achung baby, had enough material left over for Zooropa. I think this should have been a double. But then again I can only listen to Bono for a short while before his voice gets on my nerves...