For females, I think it would be Julia Roberts. Granted she has not really been active since she gave birth, her movies in the past 25 years were often big hits and she's even one of the top paid actresses (at one point, even the top paid for a single movie).
My favorite movies she made include: Mona Lisa Smile, The Mexican, Erin Brokovich, Runaway Bride, Notting Hill, Stepmom, Conspiracy Theory, My Best Friend's Wedding, Pelican Brief, Dying Young, Sleeping with the Enemy, Flatliners and of course, Pretty Woman.