I will start first, naturally. Here’s the current songlist (keyword “song”, even though there’s 1 exception) of my mp3 player, in alphabetical order:
(We are so) together [Chiba Saeko]
agony [KOTOKO]
Ai no Niwa [Duca]
Ai no Tame ni [Sakakibara Yui]
Ame no Violon [Chiba Saeko]
Ameagari [Matsushita Moeco]
Aozora loop [marble]
Asu he no Namida [Kawada Mami]
Beautiful World [Utada Hikaru]
BEGIN [Chata]
Binkan na Fuukei [Ceui]
Boku no Natsuyasumi [Satou Rina]
Brand New Breeze [kanon]
Chasse [Utatsuki Kaori]
Chiisana Tenohira [riya]
Clover Heart’s [Marie]
common wish [Yuduki]
Compass -Egao no Yukue- [Osaragi Hazumu (Ueda Kana), Kamiizumi Yasuna (Horie Yui), Kurusu Tomari (Tamura Yukari)]
cotton candy [Chata]
Daia no Genseki #brilliant covered [Chiba Saeko]
Dakishimetai [Jungle Smile]
Dango Daikazoku [Chata]
Dare mo Inai Basho [FictionJunction YUUKA]
doll (Lia version) [Lia]
doll (Tada Aoi version) [Tada Aoi]
DOLPHIN JET [Ayane]
Eien -Full Version- [Shimotsuki Haruka]
Emphatic -REVELLION- (full version) [ave;new feat.C;LINE]
enjoy summer [Yuduki]
Eternal Destiny [Sakakibara Yui]
everlasting song [FictionJunction ASUKA]
Feeling Heart [Nakatsukasa Masami]
florescence [Fujiwara Miho]
Forever Blue -akiho ver.- [Chiba Saeko]
Forever Blue [Imai Chihiro]
Fragment -Shooting star of the origin- [Chihara Minori]
Futari no Natsu [Yuduki]
Ginmokusei [ave;new feat. Sakura Saori]
H2O -utsusemi spica.- [monet]
Hajimari no Keshiki [Chiba Saeko]
Haruka Kanata [Rita]
Hatsukoi Kobako [Shimotsuki Haruka]
Heart to Heart [Nakayama Arisa]
here we stand in the morning dew [Chiba Saeko]
Hikari [Horie Yui]
Hikari no Kisetsu [Suara]
Hikari to Yami to Toki no Hate [Ceui]
Hitomi no Naka no Meikyuu [Kayou Aiko]
Hitori demo, Futari nara [Chiba Saeko]
Hoshi ga Tokete [Chiba Saeko]
I reach for the sun [Emily Bindiger]
Ice Cream [Chiba Saeko]
inside your heart [FictionJunction YUUKA]
Issei no Se [Kita Shuuhei]
Kagerou [Yuiduki Sora]
Kami-sama Onegai [Horie Yui]
Kasumi [369]
Kaze no Kotowari -Full Version- [Shimotsuki Haruka]
Kaze no Machi he [FictionJunction KEIKO]
kiss no Yukue [Anna]
KIZUNA [Ayane]
Koi no Katachi [KΛNΛ]
Koi no Mahou [ICHIKO]
Kokoro Musubi [Kokoro Musubi All Stars (Katakiri Rekka, Rekka, Yuduki, Annabel, Shimotsuki Haruka, Yuiduki Sora, Ryouka, Chata)]
Kokoro no Ato [Kosaka Riyu]
Kokoro no Tsubasa [Ceui]
Koukyuu no Taiyou [Katakiri Rekka]
Lamune-iro no Melody [Mayu]
Last regrets – Original Ver. – [Ayana]
Light colors [Lia]
Little Busters! [Rita]
Miageru Ano Sora de -‘sola’ grand ending theme song- [Yuuki Aira]
Mikansei no Story [Kazco]
Musuhi no Toki [Tomatsu Haruka]
My Green Park [Chiba Saeko]
my song [Chiba Saeko]
Narcissus [eufonius]
Natsu ga Kureta Okurimono [yozuca*]
Natukage [Lia]
Natukage -Cornwall summer mix- [Lia]
OPEN YOUR MIND -Chiisana Hane Hirogete- [Ishida Yoko]
period -winter story- [ave;new feat.Sakura Saori]
Plastic Smile Nijiiro Chorus MIX (ALBUM VER.) [Sweets Tankentai]
Plastic Smile(^^ [YURIA]
Prelude -We are not alone- [Ootou Fumi]
Prelude -We are not alone- chorus version [Instrumental]
PRIDE -try to fight!- [Lia]
PSI-missing [Kawada Mami]
Rosemary Story [Chiba Saeko]
Sajin no Kanata he [Revo & Yuki Kajiura]
Sayonara [Yato Yuria]
Sayonara Solitaire [Chiba Saeko]
Second Flight [KOTOKO & Satou Hiromi]
Shiawase no Iro [Ishida Yoko]
SHINE [L’Arc~en~Ciel]
Shinsei Philosophy ORIGINAL OPENING THEME (FULL Ver.) [Veil ∞ Yui Yamamoto]
Shoujo no Hakumei [Shimotsuki Haruka]
Sociometry [KOTOKO]
solitude [Kayou Aiko]
Sono Saki ni Aru, Dareka no Egao no Tame ni [Ayane]
Soon [Sakakibara Yui]
Sora ni Saku [Komine Lisa]
Sora no Tsuduki [Satou Hiromi]
Sore ga, Ai deshou [Shimokawa Mikuni]
Sousei no Aquarion (Element Gattai Ver.) [Apollo (Terashima Takuma), Silvia (Kakazu Yumi), Lihua (Kobayashi Sanae)]
Sousei no Aquarion (Original Ver.) [AKINO from bless4]
Souten no Mukou he [396]
still doll [Wakeshima Kanon]
Suiheisen made Nan Mile? Original Orchestra ver. [Chata]
Taiyou no Aria [Satou Hiromi]
Takaramono [Ishida Yoko]
Take me [Chiba Saeko]
Tatta Hitotsu no Omoi [KOKIA]
Tears to Tiara [Nakayama Arisa]
Tenmu no Mai, Akatsuki no Mon [KAORI]
The end of the world [angela]
Toki wo Kizamu Uta [Lia]
TOMORROW -planisphere- [monet]
Tori no Uta [Lia]
Towa no Hana [Ishida Yoko]
Tsuki to Yozora to Houkiboshi (Trance) [Ayane]
Tsuki to Yozora to Houkiboshi [Ayane]
Uninstall [Ishikawa Chiaki]
We’d get there someday [ICHIKO]
Wednesday Morning [Chiba Saeko]
Will [Komine Lisa]
will [Lia]
Yells -It’s a beautiful life- [ALI PROJECT, Ishikawa Chiaki, Ishida Youko, ELISA, GRANRODEO, Kuribayashi Minami, PSYCHIC LOVER, savage genius, JAM Project, Suara, Chihara Minori, Hirano Aya, Misato Aki, Mizuki Nana, May’n, Momoi Halko, Yonekura Chihiro]
Yoimachi Uduki -matsuri shihou image song- [Yuuki Aira]
you [Yukino Satsuki]
Yukiiro no Inori [Kusakanmuri]
Yume Haruka [Duca]
I can’t say I have included all the songs I love — in fact, there’re quite some missing, but most of those I did are definitely the best of best. You can consider this list as my recommendation of anime/game songs.