Since this is what I am famous for, I will do a sexiest at Glimmerglass list (in alphabetical order):
Philip Cutlip played Orphée in Glass' Orphée. He is lovely and quite poetical.
Jill Gardner sang a very promiscuous Euridice in Orpheus in the Underworld.
Sexiest in drag is Joélle Harvey as Cupid in Orpheus in the Underworld. There wasn't much drag work in the Orpheus cycle, so she doesn't have much competition, but she looked very cute in her little white suit, and sang beautifully.
Jeffrey Lentz sang Heurtebise in Orphée. It may have been the haircut that attracted me.
Lisa Saffer made a very seductive La Princesse in Orphée.
Michael Slattery from L'Orfeo could sell rock recordings to me any time.