Some movie actresses—like Garbo, Hepburn, Davis, and Bergman—are immortal. Long after they disappear from the planet, they remain alive in our imaginations, bigger than life. The mention of their names evokes memories of great roles and unforgettable screen moments. But when we look at the celebrated actresses of our own time, what separates those whose performances will remain vividly in our memory from those who merely catch our eye momentarily in the chorus line of today's would-be screen goddesses?

Until recently, Meryl Streep stood alone in her claim to the status of a true movie immortal. Think of her most talented contemporaries: Jessica Lange, Glenn Close, Susan Sarandon, and Diane Keaton. They entranced us, but now live mostly in memory. It's Streep alone who continues to display breathtaking range and daring, amazing us with an uncanny ability to reveal the inner life of characters as diametrically opposed as those she played in Mamma Mia! and Doubt, in Prairie Home Companion and The Devil Wears Prada.

Nevertheless, even if it doesn't show, Streep will turn 60 this year—which, while perhaps young for Clint Eastwood, is old for a screen goddess. She can't go on forever—or maybe she can (she can do anything else). But if not, who'll follow her? Who, among the current crop of stars, will carve out a special place in our psyches and regularly astonish us with the scope of her talent?

Many of the leading actresses…