From the original prog bands of the 70's like Genesis, Yes, ELP and King Crimson (I've heard Jethro Tull get thrown in there too, but I'm not feeling it)
To the later 70's bands that forged their own radio-prog style, like Saga and Rush
To 80's bands who borrowed heavily from Genesis, like Marillion, IQ and Pendragon
To heavy metal bands that took metal to new heights, like Dream Theater, Queensryche and Fates Warning
And plenty of other bands I can't quite think of off my head...