Nana Mizuki is best...

I suppose:

dream
V6
little by little
Mizuki Nana

And I'm in the same boat in that I don't understand much but it still sounds great.

The best is without a doubt T.M.Revolution. Just loves his songs. Cause he is the singer of Abingdon School Boys those songs are included also.

Ayumi Hamasaki is my favorite J Pop star ever, I have over 60 of her cds (including the mini cd singles) and vinyl and posters and calanders,.... but she is not an anime singer. If she has done any singing for an anime I would like to know. I heard she did the opening song for a PS One game,... I think it was Thousand Arms, but I could be wrong.

I don't do much research as far as who the singers of anime themes are, but my favorite anime vocalist would be Chiyako Shibahara who sang both as Beniko Komori and Miho Utsuse in Key the metal Idol. Great sound track.

Aya Hirano is also great in Haruhi and Lucky Star, get her cd "Riot Girl", its also great.

Tamaki Nami is also good.