Ayumi Hamasaki her voice is unique and a bit squeeky, but it goes well with her awesome melodies, tunes, beats, lik M, Season, and other great, catchy, emotional songs. She´s a good lyricist.
Utada Hikaru very talented, makes good music, has a cool voice, some great songs, but somehow I never got into her music
BoA Very good dancer, I never buy her albums, cause she always has 3 or 4,5 good songs on it and the rest is meh her voice is cool, has a good chance to make it to worldfame, if she can speak english more properly and if she gets a bigger chest
Namie Amuro
Very pleasant voice, good dancer, really nice, catchy songs, like ´say the word´, I thought she sang Say the world´, but anyway, ´No´ and a lot of other songs on her latest album are very cool. I bought her album.
Hitomi
Her japanese girl single was awesome, really catchy. and the lovelife version of ´there is´ rocks. She´s talented, makes good music and is a good dancer, great figure, btw.
Why the hell isn´t Mika Nakahima placed on the list?
Or Hitomi Shimatani
Or Mai Kuraki
or Chihiro Onitsuka she is kind of like a japanese Jewel, but she isn´t, she Chihiro Onitsuka with a really beautiful powerful and soulful voice, great compositions, very talented, makes very good music, pretty too.
http://www.projectj.net/here are great reviews of some artists, groups, bands who make good reviews.
Hitomi and Chihiro are on the site, as well as Shiina Ringo