This dark, sleazy, brilliantly reimagined revival is so good, you’ll want to keep coming back to the cabaret. Sam Mendes, who first directed the 1966 Kander and Ebb musical five years ago in London, populates Cabaret‘s Kit Kat Klub (the former Henry Miller’s Theatre, renovated to resemble a Weimar Republic-era Berlin nightclub) with down-and-dirty dancers and musicians. Commanding the bi-level stage as the irresistibly lewd emcee, Alan Cumming is magnetic. Whether bumping and grinding in the menage a trois number ”Two Ladies” — one of whom is a man in drag — or tenderly singing ”I Don’t Care Much” like a ’30s chanteuse, he radiates charisma. And as Sally Bowles, the spirited English singer torn between her career and a bisexual American writer (John Benjamin Hickey), Natasha Richardson projects a sweet vulnerability. She can’t belt like Liza Minnelli — and that makes her even more touching. A