He's the voice of CNN, Darth Vader, and a certain phone company. But James Earl Jones brings more than that booming basso profundo to his forceful portrayal of Norman Thayer Jr., retired English prof, emotionally distant dad, and ''old poop'' husband to Ethel (Leslie Uggams, looking far too young to pass for sixtysomething). Jones hasn't been on Broadway since 1987 his Tony-winning turn as a bitter ex-ballplayer in Fences but you'd never know it based on his quietly masterful performance, which could bring him Tony No. 3. If only Ernest Thompson's overly sentimental script which fared much better in the 1981 Oscar-winning film had held up so well.