top 10 best covers: (not in order)
Do As Inifinity - TAO
Every little Thing - Cyber Trance Presents ELT Trance
BoA - MADE IN TWENTY(20)
Tomiko Van - Senkou
Tomiko Van - Farewall
Namie Amuro - White Light / Violet Sauce
Ayumi Hamasaki - Daybreak
Seiko Matsuda - Baby's Breath
Koda Kumi - Shake It Up
Nakashima Mika - Yuki no Hana
I'll post worst list later