1. AKB/SKE/NMB/SDN/Nogizaka
2. Mizuki Nana
3. May'n
4. After School
5. Kyary Pamyu Pamyu

1. alan
2. Sodagreen
3. Ayu
4. Namie
5. Jolin

1) BREAKERZ
2) Namie Amuro
3) GLAY
4) ARASHI
5) Acid Black Cherry

Updated:

1. Ayu
2. Angela Aki
3. Ayaka
4. Koda Kumi
5. (impossible to tell at this point) PROBABLY Mai Kuraki

1) BREAKERZ
2) ARASHI
3) Namie Amuro
4) Hilcrhyme
5) SID

1. Ayumi
2. AAA
3. May'n
4. Perfume
5. Koda Kumi

This is difficult... I might update my list soon but for now:

1. ayu
2. Epik High
3. Nell
4. i11evn
5. Brown Eyed Girls

1. Perfume
2. Utada Hikaru
3. SDN48
4. alan
5. AKB48

1. Ayu (this ain't gonna change I swear)
2. Namie
3. Kuu
4. Angela Aki
5. Hikki

1.Kuu (This won't change for sure♥)
2.Ayu
3.Namie
4.Kana Nishino
5.Ai Otsuka

Current
1: Ayu
2: AKB48
3. Koda Kumi
4. Kana Nishino
5. SPEED

1) BREAKERZ
2) SPYAIR
3) ARASHI
4) Kanjani∞
5) girl next door

1) BREAKERZ
2) SPYAIR
3) Namie Amuro
4) KAT-TUN
5) ARASHI

BREAKERZ #1 ftw :love

1. Perfume
2. Ayumi Hamasaki
3. Namie Amuro
4. Utada Hikaru
5. Aira Mitsuki / Saori@destiny / Ai Otsuka

01 Koda Kumi
02 Kana Nishino
03 Ayumi Hamasaki
04 BIG BANG
05 Utada Hikaru

Based on my recent taste. :)

current ranking

1. Mika Nakashima
2. BENI
3. Girls' Generation
4. After School
5. Ayumi Hamasaki

+ Kana Nishino, Miliyah Kato, Namie Amuro

1) BREAKERZ
2) Namie Amuro
3) SPYAIR
4) KAT-TUN
5) BENI

This is really based on who I listen to more so right now though Hikki and Ayu would always be top 5.

1. Ayumi Hamasaki
2. DOUBLE
3. Mika Nakashima
4. Kumi Koda
5. Hikaru Utada

This changed a LOT... somewhat :P

1. Ayu
2. Angela Aki
3. ayaka
4. Do As Infinity
5. Koda Kumi

1) BREAKERZ
2) Namie Amuro
3) SPYAIR
4) Hilcrhyme
5) BENI