Um.....wut, lol?? First of all, the "Queen of Anime" is certainly, without a doubt, Nami Tamaki. But we won't get into all that, lol...
Ayumi only did InuYasha, right? My goodness, that anime is more famous for it's music than anything, lol! And you know why..? It's because they picked some of the biggest pop stars of the time (which, a few of them are also the biggest Asian pop stars ever, to date) to do the music. Ayumi Hamasaki was in the middle of her peak, Namie Amuro was at the end of her peak, BoA was just starting out in Japan (which also happens to be the beginning of her peak), hitomi was in the middle of her peak, Do As Infinity had just started to peak..... You get my point, yes?
A lot of Westerners found out about Ayu, Namie, BoA, and Do As Infinity (and Dream, and probably all the others, too) through either this or another theme song they may have done, but that's normal. That's how most Westerners find out about J-Pop. Even somebody as huge as Hikaru Utada was completely unknown in Western world to even a lot of J-Pop listeners until Kingdom Hearts. Kinda disappointing, but that's just how it is. The difference between most of these mega-stars (with maybe the exception of DAI and Dream) is the fact that you CAN find HUGE hits from every one of them, without running into an anime. Ayu, of course, has countless number ones many will find her through, Namie has songs like CAN YOU CELEBRATE?, Hikki has Automatic, etc...