Here's a search string that led to my page:
"Is Renee Fleming a better singer than Kiri Te Kanawa is or was?"
Renee Fleming was, until several years ago, a better singer than Kiri te Kanawa is now, primarily in that Kiri te Kanawa barely sings now and that's no good at all. RF now is certainly a worse singer than KtK was at her best, except when (occasionally) she's really good again, like in those Berg songs at Carnegie.
Some days RF is a worse singer than KtK ever thought about being, like when she's singing in a Southern accent, which KtK would never do, I'm guessing, or when she's singing jazz, which KtK did in a less misguided and grating way than RF. Te Kanawa, at her worst, was just dull. One of the crew at Parterre dubbed her "The World's Highest Paid Church Soprano," but then she went and sang that final run of Capriccio at the Met that (all snarkitude dropped for a moment) brought tears to my eyes at the outburst of "Madeleine!" in the final scene. Follow that link, by the way, and you'll also find the witty potshot about how K's Tosca is the only one you'll ever hear described as "soothing."
We could always compare them in certain roles. I, as much as anyone, like occasionally reducing opera to little more than the sausage race at a Brewers game.
Desdemona: Fleming wins.
Countess in Figaro: te Kanawa wins, unless it's Fleming fifteen years ago in which case it's a draw
Mimi in Rent: Neither of them ever sang it but wouldn't it be hilarious?
Effie in Dreamgirls: Oh stop, now you're just being silly.
Vanessa: Kiri was supposedly pretty good but Fleming hasn't sung it and I guess won't be offered it at the Met because they haven't staged it since 1965. *tap tap tap* Is this thing on?
So there you have it. Don't you love it when the internet provides an objective answer to your question?
Another disappointed reader googles his way here with the search string "words lamento della ninfa." Well I don't know them, of course, but I'm happy to make some up.
Ahime, com'e triste d'essere ninfa!
E ninfere qua e la, notte e giorno
Senza gia il tempo per fare altre cose!
Ahime, non vuoglio essere piu ninfa,
Ma che puo fare? Cantaro un lamento, cosi,
E forse Signore Monteverdi puo lasciare
La sua opera somnifera e interminabile di Poppea
Per due momenti, e scrivere le note
Per una povera ninfa, cantante suo lamento, ahime, senza musica.
Nymphs speak lousy Italian, as it turns out. One supposes they speak Nymph. I do hope ninfa means nymph, or I'm going to look like I'm not serious about these matters.