Reviewing a work like South Pacific or a star like Robert Goulet seems, in a way, like an exercise in futility; both are products of a bygone era, and they really don't make 'em like that anymore. But if an audience attending this touring production is prompted to reevaluate the standards by which it judges current entertainment, that's all to the good. Since making his Broadway debut in 1960, Goulet has had sizable ranks of both admirers and critics; that's what happens to a performer with such a distinctive vocal instrument and individual style. Singer-actors like Goulet are few and far between, especially in this day of interchangeable musical-comedy robo-gypsies; despite a slight sogginess in his tone, Goulet in middle age remains an artist of deep and solid musical authority, with a gentle boyishness of manner to offset the rich virility of his voice. As for South Pacific itself, Oscar Hammerstein and Joshua Logan's 1949 libretto now seems terribly old-fashioned in its sentimentality and in the obviousness with which it sets up song cues; but the script also comes to terms with human nature's darker impulses in a wise and quiet way. In this story of American sailors in Polynesia during the waning days of World War II, there are no "good guys" or "bad guys": rather, we have met the enemy and he is us--our capacity to betray our own better impulses and best interests through racial prejudice, economic exploitation, and sexual insincerity. And the talent and craftsmanship evident in Hammerstein and Richard Rodgers's score--one perfect and memorable song after another--are never out of fashion. Chicago Theatre, through March 27. Tuesday-Sunday, 8 PM; matinee Saturday and Sunday, 2 PM. $9.50-$33.50.