LMAO, if we go by sales and status, that obviously the one and only Utada Hikaru wins!
01.Utada Hikaru
02.Ayumi Hamasaki
03.Koda Kumi (her ****tyness has catapulted her to new heights)
04.BoA (surpassed by Koda Kumi in recent years, but literally a national embassador and the biggest in Asia overall...that and she's hott!)
CC: Namie Amuro (the only Hip-Hop star in Japan) and Mika Nakishima (generic).
Kworb, the signature song for Utada would be either "Sakura Drops" or "First Love" IMO...good job on the rest though I guess.