id say all 3 bands (immortal, emperor, and dissection) are very close when it comes to quality and importance. they just did different things. emperor has the classic symphonic black metal sound. dissection includes a DM riffing style while still maintaining an overall black metal sound. and immortal really pulled off the BM atmosphere without the need to constantly grind and shriek, maintaining some slow melodic pieces (not groove) that other bands like mayhem and darkthrone had not achieved.
so what it boils down to is which you like better, but i think we can all agree that cradle of filth is nothing significant.
~gR~