MM and M10M about tied for first place. I guess I'd say I listen to M10M a little more since they're still active and I have more of their CDs.
After that Gackt, and then Schwarz Stein and Kaya. I haven't really liked any Kaya releases since Carmilla, otherwise he might have secured a higher spot.
The ones i listen to the most are MM, Kozi, Gackt, M10M, there is a while that i don't listen to Eod, nil, Klaha, or Tetsu solo, but i like them too. I like some Kaya and SS songs, not a big fan. And I am not a fan of Hora solo.