Recently, a number of people have been making lists of favorite female seiyuu. Although Megumi Hayashibara and Kikuko Inoue have been mentioned, the lists generally focus on recent favorites, e.g. Aya Hirano. Here is a trio of experienced voice actresses who would be on my list.
Kotono Mitsuishi — One of the great comic actresses. Besides such silly roles as Usagi Tsukino and Excel Excel, she also is effective in straight roles such as Ginger in Sugar and Mireille Bouquet in Noir.
Aya Hisakawa — Outstandingly versatile. Her roles range from the demure Ami Mizuno in Sailor Moon to the anything-but-demure Mune-Mune in Abenobashi, not to mention Kerberos in Cardcaptor Sakura and Chloe in Noir.
Houko Kuwashima — Another versatile actress, when she isn’t stuck playing yet another emotionless girl. Her roles range from the ditsy Yurika Misumaru in Nadesico to the spirited Shuurei in Saiunkoku Monogatari to the tough Isako in Denno Coil. And, of course, there’s the definitive emotionless girl, Kirika Yumura.