Never was that big of a Hikaru Utada fan. I did really like "Simple and Clean"/"Hikari" from Kingdom Hearts and "Movin' On Without You" but other than that, she didn't really leave much of an impression on me. When I discovered Shiina Ringo, however, I haven't been the same since. She has turned my music world upside down.
I was always more of an Ayumi Hamasaki guy anyway. But looking back on her now, Shiina Ringo has her outclassed in every regard, IMO. Unfortunately, she does not have her number of fans.