Susan Sarandon as Sister Helen Prejean in Dead Man Walking. Susan Sarandon usually plays a modern woman in touch with her own sexuality, even if she's not especially introspective. As Sister Helen, she reverses it -- playing a compassionate nun who struggles mightily to understand everyone around her, almost all of whom are in unfathomable pain, while trying to figure out the right thing to do.
Diana Ross as Billie Holiday in Lady Sings the Blues. I have been a big fan of MIss Ross' for as long as I can remember, and I'm fascinated to hear her act while she sings in this movie. She dials her own Motown/girl group exuberance way, way back and her turns at the mic take on the anesthetized quality that bespoke Lady Day's pain.
Reese Witherspoon as June Carter in Walk the Line. The comedienne from Legally Blonde and Sweet Home Alabama was replaced by a three-dimensional woman under pressure -- making her way in a competitive profession while trying to live up to the expectations of a public who believed they knew her famous family and suffering through her love for a married man. She's both a church-going mother and a serious artist, as well as a love interest, in this movie and she's awesome.