Okay, seeing as I seem to have different tastes than most people here I just want to say that I can take basically any kind of music that you throw at me except for lame American boy bands from the 90s (I'm looking at you N'Sync and Backstreet Boys!)
As for JMusic, if you like background music Yuki Kaijura is pretty good.
For JPop I enjoy KOTOKO,
Under17 (who has sadly broken up),
Funta (who did a cool collaberation song with Under17 called 'Gemstone'),
Rie Tanaka (she was Lacus Clyne, Meer Campbell, and Chii),
savage genius (OP and ED for Uta~Kata),
and Round Table (feat. Nino) (who has done a lot of OP and EDs for shows including: Chobits, Welcome to the NHK!, Gunbuster 2, and Uninhabited Planet Survive).
I came into contact with these artists through anime OPs, EDs, and insert songs, so I would recommend that, even though it may not be the top tier of music in Japan, it could give you a reason to scout out more JBands that you want to listen to. So get to it and experience the magic of Japanese music!
