Nancy Argenta (stage name of Canadian soprano Nancy Herbison) is my favourite singer, but I get the impression she's not a popularity superstar among music fans. There's something about her voice that I just love; I even listen to J.S. Bach if she's singing it. I first discovered her listening to her as Zerlina in Norrington's Don Giovanni recording on EMI; I still think this is her best recording to date. I recently obtained a few more difficult to get CDs, like Argenta singing Schubert lieder and a complete Haydn's Die Schöpfung. I'm hoping to get all her non-Baroque recordings, but sadly (from my perspective!!) that happens to be her focus. I'm still lacking the R.Strauss "Four Last Songs", and maybe other stuff I don't even know about.
My other favourite singers are people like Kathleen Battle (who's not quite the same type as I'm talking about), a rarely heard Hungarian named Edit Károly (maybe in raw sound the most beautiful voice I've ever heard), and so on. Who else is like this? So far, the only name I've ever gotten back when asking elsewhere is Emma Kirkby. I find her pleasant for, oh, 3 minutes, then her voice grates on me, and I don't know why. But yes, she's the same "type". I haven't really found anyone else with a voice of that sort.