I've made three lists in order to split some hairs:
Great Singers with Great Looks: Grace Jones, Susanna Hoffs, Ann-Margret, Vanessa Williams, Dolly Parton, Cher, Marilyn McCoo, Sade, Julie London.
Great Singers with Good Looks: Nancy Wilson of jazz fame, Lisa Stansfield, Kate Bush, Dame Shirley Bassey, Taylor Dayne, and, yes, Whitney Houston.
Good Singers with Great Looks: Jody Watley, Cathy Dennis, Belinda Carlisle, Kim Wilde, Nancy Wilson of Heart, Shania Twain, Sophie Ellis-Bextor, Lauren Christy, Rosie Vela, Faith Hill, Kim Carnes, Sheena Easton, Kylie Minogue, Natalie Imbruglia, Olivia Newton-John, Dana Glover, and, yes, Debbie Harry.
So glad that in the prior posts a few had the decency to mention Jody Watley (who was truly like a modern day Nefertiti in her 80s heyday), Vanessa Williams and Lisa Stansfield. By the looks of these 400+ posts, it would seem that Debbie, Whitney and Sheena are in the lead.
For anyone who has never come across Dana Glover, please watch THIS (and gather your smelling salts beforehand if they are near):