If we're talking about brilliance in terms of innovation and originality, etcetera, then these are the bands:
Neurosis: They progress, they're completely original, great musicians, etc, etc. Nuff' said.
Isis: same as Neurosis, but not as good IMO...but to be as good as Neurosis is impossible
Arcturus: Very original and innovative, eh?
Enslaved: The past two albums from these Norwegians, "Mardraum: Beyond The Within" and "Monumension", have been absolutely phenominal, covering all the areas of 'brilliance'.
There are others. Many of the bands other people said are very good, (ie. Katatonia, who are actually amazing), but I don't know if they could be called brilliant.
Also, just because you're original and innovation doesn't make you brilliant.
Just my $0.02.