-Ayumi has a very emotional voice and a good range, back in the begining of her career, she would be the worst on this list, nowadays she isn't an amazing vocalist, but is a very good one. Her very hated vibrato is actually very hard to do... 3,5/5
http://www.youtube.com/watch?v=9ZOJRTALn40
-Hikaru has a very good range and most of the time her vocal improvisation is very good, but she gets out of breath easily and can't always reach the high notes. Even so, when she is good, she is GOOD. 3,5/5
http://www.youtube.com/watch?v=SfUx-nWG21Y
-Koda... sorry people who loves her vocals, I just hate them! On fast songs she is just plain horrible (btw, fast songs are harder to sing than ballads), and she screams a lot while singing her ballads, don't see anything special with her range too... 2/5
http://www.youtube.com/watch?v=Yv6cQ...eature=related
-Namie... very beautiful low notes, lots of sufering to reach the high ones... I wish her songs where lower so she could show the best of her voice... 3/5
http://www.youtube.com/watch?v=cZOtwOLGLqg
-Mika... Goes off-key a lot, can't properly reach the high notes (but at least she shows some emotion when she gots hurt by trying to reach them), breath problems... very beautiful low notes even so... 2/5
http://www.youtube.com/watch?v=jQBD6...eature=related
I don't follow Koda's and Mika's career, maybe they are better now and I just don't know...
So... even if I'm a biased Ayu and Hikki fan, can't vote for them cuz even if IMO they are the best on this list, they are far from being amazing vocalists... My vote would go for either Hitomi Shimatani (
http://www.youtube.com/watch?v=e_pBt...eature=related), Ayaka Hirahara (
http://www.youtube.com/watch?v=L9UWh780V7Y), Alan (
http://www.youtube.com/watch?v=6bWLm...eature=related) or Akina Nakamori (
http://www.youtube.com/watch?v=uX9xJRE_L7c)... And Rina Aichi (
http://www.youtube.com/watch?v=sQtvnNEHSJs) on the more popish/"I'm not a ballad singer" side... Yuna Ito, the Superfly girl, Ayaka are also better than anyone on that list, but I don't know their work...
btw: I HATE youtube covers! they make it almost impossible to find live performances from the actual singer, and most of the covers are pretty bad ~~'