Answer
The Oscar-winning song that Christopher Cross performed is titled "Arthur's Theme (Best That You Can Do)", a poignant ballad featured in the 1981 romantic comedy-drama film "Arthur," starring Dudley Moore and Liza Minnelli. The song encapsulates the essence of the film, conveying the protagonist's journey of introspection, growth, and finding true love, all while captivating listeners with its soulful melodies and heartfelt lyrics.