Although they aren't bad, I think Pagan's Mind gets far too much praise in some prog metal circles.
Radiohead ?
Mayhem's Rom 5:12 rulez
I vote for Pink Floyd. Not that they aren't great, I just don't think they're the epitome of musical innovation and genius, as so many people seem to believe. (If I spontaneously combust after posting this, you'll know that the Gods have struck me down and I should not have blasphemed.)
Nowadays, listening to Pink Floyd probably wouldn't seem like anything that special. In their day though, I think they were pretty influential and innovative.
Alexi Laiho writes like some war hungry 10-year-old about to go slay some Horde on World Of Warcraft.