Um...well what have you been exposed to?
Well, I've listened to pretty much all of the big names (i.e. Emperor, Satyricon, Immortal, etc.), but a lot of them were a long time ago, and I didn't really give them much of a chance. I'll list the albums I've heard very recently:
Drudkh - Autumn Aurora
Drudkh - Blood in Our Wells
Mayhem - Dawn of the Black Hearts
Mayhem - De Mysteriis dom Sathanas
Nokturnal Mortum - Lunar Poetry
Darkthrone - Soulside Journey
Darkthrone - Goatlord
Darkthrone - Under a Funeral Moon
and, of course, the Dimmu Borgir discog
Besides the Dimmu albums, which seem to me leagues above the others in terms of melody, I do enjoy the Darkthrone ones - though there are very few songs from them which really stick in my head. Of those, "Cromlech" is by far the best. The rest of
Soulside Journey just doesn't seem to hold up to that song.
The Mayhem albums I can't remember a single melody from. The Nokturnal Mortum album actually had some memorable riffs (the main one from "Perun's Celestial Silver" comes to mind), but on the whole it was still pretty hit-and-miss.
I did enjoy Drudkh's
Autumn Aurora, and have listened to it a number of times. The melodies are tolerable, but they all seem to have a similar dreary quality to them which isn't really all that catchy.
My favorite riffs on the album are the two that are used in the closing song, "The First Snow". I think they're both fantastic, as well as the blurry guitar tone with which they are played. Except there are only
two of them, and they're both repeated about 96 fucking times throughout the song, with
no variations and
no lead guitar embellishments.
So that's basically been my experience with black metal as of late. As I said, if you think I'm missing any bands in the genre with particularly great melodies, do let me know.