heh, maybe you guys haven't heard good grunting. =) Cryptopsy's Lord Worm was a very boring grunter. It can be done far better...of course, to achieve an interesting aesthetic with grunting, you generally have to abandon representing lyrics even more than Lord Worm did.....grunts are good when they sometimes turn into deep or high-pitched croaking dynamically during the song, or when the grunting becomes noticably rhythmic with the song. You wouldn't think it from listening to early Cryptopsy and hearing everyone worship Lord Worm as the best grunter....but grunts can get to be extremely dynamic and varied. I don't mean to sound elitist, but generally, the more underground you go, the more kinds of grunting you'll notice. ;o)
What everyone said about growling though i'll agree with; especially in the case of Mikael's growling. The best kind is definately when the lyrics are clear too; it's strange hearing such a demonically low voice spouting discernable human language. It makes the sense of evil (or the feeling of evil) much more malevolent when it wears an intimate human disguise. It's a parallel comparison to say how realistic danger (say in movies and games) is usually a lot scarier than sci-fi scares like made-up monsters etc.
Overall....i'm straying more to grunts right now. Stuff like Debodified, Devourment and early Neuraxis have gotten me really interested.