So this is what she meant by embracing your self-worth! Oprah Winfrey just became the first female African-American billionaire and the first female entertainer to land on Forbes' list of the world's wealthiest people. The recession helps explain why this year's roster is shorter than 2002's, but that won't keep Hollywood from fixating on the ultrarich. Martin Scorsese is preparing to direct The Aviator, in which Leo DiCaprio will play Howard Hughes. Fox is developing a live-action Richie Rich pilot written by Chris Kelly (Grounded for Life). ''We're in uncertain economic times,'' says Kelly, ''and people like that fantasy of limitless resources.'' And now there's hope for the rest of us: Who Wants to Be a Millionaire producer Michael Davies is betting on a new show for The WB in which contestants compete for a potential billion-dollar jackpot. Oprah, watch your back.