I would approach question in two ways. One being simply who is good vocalist, but then also projects what would be the project without the voice, just as music. Like, later days CONSUMER ELECTRONICS or WHITEHOUSE. The vocals are the song, basically. They are notable for sheer insanity of delivery, but also that they are the song.
As opposed you could listen to certain other bands and think, without vocals it would be good track. Perhaps even better.
If we set standard to somewhere like Con-Dom, it puts standard pretty damn high. It is hard to think some aggro hardcore yelling drenched in efx would be notable next to that. His sound is instantly recognizable, there is vast expression from talk, preaching in sermon style, aggressive and violent shouting. Always with sense of timing and tension. Not technical vocals by any means, but applying vocal style according to mood and style of the sound material.
These are obvious of course. I would put among very notable voices:
SODALITY
ULTRA
GENOCIDE ORGAN
ANENZEPHALIA
Two latter ones neat example how theoretically anyone can buy the effects and synths, but nobody sounds like Anenzephalia, especially his trademark voice and cold eerie delivery of the voice.
