I can't choose, it's so hard, but alan is on my list

They are in no specific order.

1.Ayumi Hamasaki- Memorial Address
2.Utada Hikaru- FINAL DISTANCE
3.G-Dragon-She's gone
4.Utada Hikaru- Prisoner Of Love
5.BigBang- My Heaven
6.Brown Eyed Girls- Abracadabra
7.After School- Because of you
8.f(x)- NU ABO
9.DBSK- Love in the ice
10.Marie Digby-Gravity

1.HEAVEN/Ayu
2.Goodbye Days/YUI
3.Futari/Ikimonogakari
4.Glamurous Sky/Mika Nakashima
5.You Were..../Ayu
6.STEP you/Ayu\
7.SEASONS/Ayu
8.is this LOVE_/Ayu
9.SURREAL/Ayu
10.evolution/Ayu

Oh this is hard D:
In no particular order:

1)Birdcage- Gackt
2)I love you- Yutaka Ozaki
3)Fare Well- Larc'~en~ciel
4)I am... Ayumi Hamasaki
5)Love in the Ice- Tohoshinki (TVXQ)
6)Can you Celebrate-Namie Amuro
7)First Love- Utada Hikaru
8)Kono Daremo Inai Heya De- Gackt
9)Endless Rain-X Japan
10) Song for XX-Ayumi Hamasaki

1. YES - Hiromi
2. don't look back - Ayumi Hamasaki
3. Aishou - Koda Kumi
4. Duty - Ayumi Hamasaki
5. Swing - Lee Hyori
6. Girls on Top - BoA
7. you - Koda Kumi
8. JEWEL - Ayumi Hamasaki
9. Chitty Chitty Bang Bang - Lee Hyori
10. Crystal Girl - ICONIQ

They're not totally in order, but I love all these songs.

1 Kingyo hanabi _ Ai Otsuka
2 SEASONS and End roll _ A.Hamasaki
3 Oh! my god _ Mayday
4 Motto... and Aitakute x2 _ Kana Nishino
5 Ai uta _ Greeeen
6 Meri kuri _ BoA
7 Wu yue tian_ S.H.E
8 Sakurairo maukoro _ Mika nakashima
9 SURREAL and evolution _ A.hamasaki
10 Planetarium_Ai otsuka

in no order. and not that much different from last time. Just changed two songs.

宇多田ヒカル - Passion
黒木メイサ - SHOCK -運命-
倖田來未 - TABOO
capsule - JUMPER
doping panda - beat addiction
MiChi - PROMiSE
GACKT - REDEMPTION
安室奈美恵 - WHAT A FEELING
JASMINE - sad to say
浜崎あゆみ - STEP you

1. Depend on you- 浜崎あゆみ
2. HOME- B'z
3. Dolls- 浜崎あゆみ
4. TABOO- 倖田来未
5. MY LONELY TOWN- B'z
6. GO- 稲葉浩志
7. O.NO.RE- 稲葉浩志
8. 炎- 稲葉浩志
9. The Morning Call- 稲葉浩志
10. ねがい- B'z

(WOW!!! My list is B'z dominated, isn't it?? :laugh)

not sure if i like them most but they are certainly most played on itune
jpop only

1. ash like snow -brilliant green
2. blossom -ayu
3.絆-kizunairo-色 lia
4.愛は暗闇の中で zard
5.flower of bravery fripside
6.会いたくて 会いたくて kana nishino
7.Nyan Nyan Special Service Medley (Tokumori) macross duo
8. eternally- utada
9. together when ayu
10.glamorous sky mika nakashima

No order
Ayu - ourselves
Ayu - CAROLS
Ayu - INSPIRE
Ayu - Sparkle
Ayu - HANABI
Ayu - Mirrorcle World
Ayu - ANGEL'S SONG
Angela Aki - kiss me goodbye
Ami Suzuki - free free
Namie Amuro - Wild

1.SURREAL (Ayu)
2.Passion (Hikki)
3.HEAVEN (Ayu)
4.Don't Leave Me (Abe Mao)
5.Goodbye Happiness (Hikki)
6.A Song for XX (Ayu)
7.Dearest (Ayu)
8.M (Ayu)
9.End roll (Ayu)
10.TOKYO (YUI)
11.Stay Gold (Hikki)
12.You Were... (Ayu)
13.Take 5 (Hikki)
14.Heartbreaker (G-Dragon)
15.Glamorous Sky (Mika Nakashima)
16.MY ALL (Ayu)
17.TABOO (Koda Kumi)
18.Futari (ikimono gakari)
19.Say The Word (Namie Amuro)
20.BLUE (Hikki)

No order
BEG Abracadabra + Candy Man
T-ara One & One + It hurts
Girl's Day Nothing Lasts Forever
Namie Amuro Wild
Ayumi Hamasaki Fairyland + Boy & Girls
... ft. Hyorin Magic Drag
SNSD Mr. Taxi

Tbh, if I was able to chose unofficial remixes, this list would at least partly be different.
Nothing from this year, since I can't properly judge yet if I continue liking certain songs.

1.ayumi hamasaki - BRILLANTE
2.ayumi hamasaki - HEAVEN
3.ayumi hamasaki - RAINBOW
4.LANDS (Akanishi Jin) - Hatachi no Sensou + Hatachi no Sensou -Y's edition-
5.Yamashita Tomohisa - One in a million
6.KELUN - Howling Heart
7.Kou Shibasaki - PARALLEL WORLD READING
8.Miliyah Kato - ROMAN
9.ayumi hamasaki - HANABI ~episode II~
10.Tiara - Arigatou. Aishiteta Hito
---------------------------------
11.Namie Amuro - Come
12.Chiharu Tamashiro - 神様
13.Yo Hitoto - 愛と誠のファンタジア
14.Yamashita Tomohisa - Touch You
15.Meisa Kuroki - Wired Life
16.NEWS - Why
17.Yoshikuni Dochin - Failure
18.B'z - 今夜　月の見える丘に
19.Utada Hikaru - Show Me Love (Not A Dream)
20.SPYAIR - 0 GAME
21.MAA - OKay
22.ayumi hamasaki - Love song
23.ayumi hamasaki - Virgin Road
24.Jin Akanishi - Seasons
25.Miliyah Kato - DESIRE
26.AI - Independent Woman
27.EXILE - Rising Sun
28.KAT-TUN - RESCUE
29.KAT-TUN - ONE DAY
30.Masaki Yuka - Change Myself

Omg... I have thousand of all time favorite songs :thud

1. Utada Hikaru - Passion
2. EA - UCHU
3. no.9 - bug beats
4. ayumi hamasaki - surreal
5. ayumi hamasaki - monochrome
6. MAA - Tommorow @ your Kingdom
7. Emi Hinouchi - Grow
8. Mademoiselle Yulia - MIDNIGHT EXPRESS
9. Utada Hikaru - Take 5
10. SNSD - Gee :D

My top ten would probably just be songs from Dir en grey and Ayumi Hamasaki.

I'll just keep it at that so I don't give a bunch of similar answers.

Wah, this is really hard. :thud

Maaya Sakamoto - Kiseki no umi
Maaya Sakamoto - 私は丘の上から花瓶を投げる
2NE1 - I am the best
Big Bang - Fantastic Baby
X JAPAN - Drain
Luna Sea - Rosier
OK ONE ROCK: Re:make
Naomi Kaitani - In this distant town
Gackt - Returner
Ayumi Hamasaki - STEP You

I'll limit myself to Jpop to make this easier for myself. Plus list each artist only once.

1. Chihiro Onitsuka - Tiger in My Love
2. Utada Hikaru - Stay Gold
3. Ayumi Hamasaki - JEWEL
4. kz (livetune) ft. Miku Hatsune - Yellow
5. YUKI - Wakusei ni Nore
6. BoA - Shine We Are!
7. Shoko Nakagawa - Calling Location
8. SWEET BLACK feat. Maki Goto - with...
9. Shiina Ringo - Tsumi to Batsu
10. JASMINE - CLUBBIN'

1. Memorial Address - Ayumi Hamasaki
2. A Song for XX - Ayumi Hamasaki
3. HANABI - Ayumi Hamasaki
4. HEAVEN - Ayumi Hamasaki
5. RAINBOW - Ayumi Hamasaki
6. Sakurairo - Angela Aki
7. Tempest - Namie Amuro
8. Do Me More - Namie Amuro
9. No Man's Land - Koda Kumi
10. Love Technique - Koda Kumi

In a specific order... ;3

1. 下田麻美 - 炉心融解
2. Lia - 鳥の詩
3. 大塚愛 - ゾッ婚ディション
4. 島みやえい子 - FLOW
5. SeleP - Gothic Dance (Vocaloid song)
6. MOMO - DROWNING -Ghetto blaster style-
7. MEG - DESTINATION
8. ももいろクローバーZ - 猛烈宇宙交響曲・第七楽章「無限の愛」
9. 島みやえい子 - Fortress
10. KOTOKO - Abyss