Here's my list, mixed with bands and artists lol:

01 Koda Kumi
02 Lee Hyori
03 4minute
04 BoA
05 Namie Amuro
06 Utada Hikaru
07 KAT-TUN
08 Ami Suzuki
09 Mai Kuraki
10 Ai Otsuka
11 2NE1
12 NEWS
13 Anna Tsuchiya
14 Hey! Say! JUMP
15 MEG
16 Crystal Kay
17 Aira Mitsuki
18 AI
19 Ayumi Hamasaki

There. So true. :D:D

1.Ayumi Hamasaki
2.Namie Amuro
3.YUI
4.Kana Nishino
5.Ikimonogakari
6.Utada Hikaru
7.Koda Kumi
8.Aya Kamiki
9.Angela Aki
10.alan
11.Mika Nakashima
12.Yui Aragaki
13.SNSD

1 snsd
2 big bang
3 tae yang
4 4minute
5 b2st
6 2nel
7 2pm
8 f(x)
9 t-ara
10 shinee
11 suju
12 kara
13 kana nishino
14 dbsk
15 ppl i forgot x.x

um I have sooo very many...I'll just stop the list at 30. It's kind of hard to rank them...only like, the first 7 or so are in order lol

1. Koda Kumi
2. Ayumi Hamasaki
3. Utada Hikaru
4. Emi Hinouchi
5. Eiko Shimamiya
6. audio safari
7. Namie Amuro
8. Lena Fujii
9. Clazziquai Project
10. Dolce Triade
11. capsule
12. immi
13. Ami Suzuki
14. MAI / Ruppina +
15. mink
16. Mizca
17. ICONIQ
18. Spangle Call lilli line
19. Hiromi
20. Rie Fu
21. YMCK
22. Akino Arai
23. akiko
24. Floor on the Intelligence
25. arlie
26. Emiri Miyamoto
27. Piana
28. JASMINE
29. Tiana Xiao
30. Texas Pandaa

These are Japanese artists only...maybe some korean.

1. Ayumi Hamasaki
2. Koda Kumi
3. Lee Hyori
4. ICONIQ
5. Hiromi
6. DOUBLE
7. BoA
8. SE7EN
9. Jolin Tsai
10. Namie Amuro

Only the Japanese artists, I guess.

1. Hamasaki Ayumi (forever and ever :heart)
2. Onitsuka Chihiro :heart
3. Sakamoto Maaya
4. Tate Takako
5. alan
6. Oku Hanako
7. Day After Tomorrow
8. Every Little Thing
9. Shiina Ringo
10. Arashi

Only Asian artists:

My Top 10 atm:

1. Ayumi Hamasaki
2. Perfume <3333333333333333
3. Tomoko Kawase (more specifically, her february6 persona but I like some of her other stuff as well)
4. Kalafina (Hikarrruuu!!! :heart Yuki Kajuira is a genius I swear)
5. S/mileage (been listening to the singles non-stop to prep myself, cannot wait for the album <3)
6. Mini Moni
7. dream (original 3 member, dear... is one of the best albums ever kthnxbi)
8. Koharu Kusumi (not really a singer anymore but I love the stuff she did for H!P nonetheless and still listen regularly)
9. Buono!
10. SNSD

People I also like but can't rate (yet):

W
Aya Hirano
Berryz Kobo
Namie Amuro
Utada
PUFFY
KOTOKO
DEF.DIVA
alan
AKB48
Momosu
4minute
Pink Lady

My favourite asian singers:

1. Koda Kumi
2. 2NE1
3. Ayumi Hamasaki
4. Jolin Tsai
5. Hyori Lee
6. Munehiro
5. Nana Tanimura
7. Jasmine
8. Mucc
9. Olivia
10. Ami Suzuki
11. Namie Amuro
12. Dream

1. V6 / Yiruma
2. Ayumi Hamasaki
3. Ai Maeda
4. Wada Kouji
5. SINCREA
6. GACKT
7. Masato Nakamura
8. Koda Kumi
9. Namie Amuro
10. KOTOKO

Okay, I'm going to try and make mine, but I'm including non-Japanese singers.

1. sifow
2. Ayu
3. Kuu
4. Daft Punk
5. Britney Spears
6. Kana Nishino

From here on, they are subject to change, depending on mood or future releases.

7. mini
8. SuG
9. Perfume
10. twenty4-7
11. SHION
12. Hidemi Uematsu
13. Aira Mitsuki
14. capsule
15. LM.C
16. Miray
17. hiromi
18. ViViD
19. The Kiddie
20. Gwen Stefani
21. Shoko Nakagawa
22. Miliyah Kato

I think that's it...

1.Koda kumi
2.Namie amuro
3.Amano tsukiko/amano tsuki
4.Utada Hikaru
5.Ayumi hamasaki
6.Lee hyori
7.Nana kitade
8.Ai otsuka
9.4minute

1.- OLIVIA
2.- alan

a distant 3.- Ayumi Hamasaki

Not subject to change.

1. Utada Hikaru
2. Namie Amuro
3. Ayumi Hamasaki
4. Koda Kumi

Subject to change

5. JASMINE/Meisa Kuroki

Favorite japanese singers/groups

1. OLIVIA
2. Ayumi Hamasaki
3. Miliyah Kato
4. ORIGA (not really japanese, but let's just say that she counts!)
5. DAI
6. capsule
7. Changin' my life

Just what I feel like, atm. No. 1 and 2 NEVER EVER changes though.

wow, this is gonna be hard

01. ayumi hamasaki
02. Tohoshinki
03. SHINee
04. BEAST
05. SNSD
06. 2PM
07. Super Junior / BoA
08. T-ara
09. After School
10. Lee Jun Hyung / IVY
11. Kara
12. Son Dam Bi
13. Seo in Young
14. 4Minute
15. Lee hyori
16. SG WANNABE
17. Kangta

Top favorites, not really inclined to change for awhile
1.Hamasaki Ayumi
2.Namie Amuro
3.Chihiro Onitsuka
4.Koda Kumi
5.Mika Nakashima
--------------------
Really love these artists, but in no exact order
6.Miku Hatsune (VOCALOID)
7.Alan
8.Abingdon Boys School
9.Corrine Bailey Rae
10.Tommy February/Heavenly6
11. Morning Musume
12.Crystal Kay
13. Alicia Keys
14. Masami Okui
----------------
Other Artists that I really like, but I haven't gotten too into yet/don't listen to as much
15.Utada Hikaru
16. Sowelu
17. Yui
18. Kana Nishino
19. Lady Gaga
20. Gackt
21. Boa
22. Tohoshinki
23.HIGH AND MIGHTY COLOR
24. Ai
25. Yuna ito
26. Perfume
27. T.M. REVOLUTION
28.Beyonce
29. M-flo
30. Maraiah Carrey(sp?)
31. Kelly Clarkson
the list goes on and on

GOD:
1 & 2. Shiina Ringo / Tokyo Jihen :heart

ROYALTY:
3. Ayumi Hamasaki

the order of the rest is ever changing:
4. GO!GO!7188
5. alan
6. Cocco
7. Salyu
8. Plus-Tech Squeeze Box
9. Bonnie Pink
10. Morning Musume (*shame*)

1.AYU
2.KUU
3.NAMIE
4.AI OTSUKA
5.ALAN
6.AURAL VAMPIRE
7.TOMMY HEAVENLY6 and frebruary6(tomoko kawase)
8.YUI

Here's my top 5 :
Ayumi Hamasaki
Ai Otsuka
Kana Nishino
Southern all stars
Every little thing

1.ayumi hamasaki
2.koda kumi
3.namie amuro
4.alan
5.mika nakashima
6.nishino kana
7.Tsuchiya Anna
7.Miliyah Kato
8.BoA
9.otsuka ai
10.aya ueto
11.hitomi
12.Def tech
13.Suzuki Ami
14.Kaela kimura
15.Ikimonogakari
16.MEG
17.AZU
18.Kuroki Meisa