The brightness and shine of a diamond earring are determined by the quality of the diamond, as well as the quality of the cut. A diamond that is cut well will reflect light more effectively, making it appear brighter and more radiant. Additionally, diamonds that are of higher quality and have fewer blemishes and inclusions will also tend to shine more brightly. Ultimately, the diamond earrings that will shine the most are those that are made with high-quality diamonds that have been expertly cut.