Krishna is maintaining unlimited relationships with unlimited devotees and with all these unlimited devotees Krishna is having a variation of relationships and all are dear to Him. It is not that any living being is not dear to Krishna. Krishna is described as a friend to all living beings. So Krishna maintains relationships with all devotees and everyone is dear to Him .... but Srimati Radharani is the most dear of all. She is the personification of the (Sanskrit)..shakti, the pleasure potency and this pleasure potency is actually relating to devotional service. Devotional service is the pleasure potency .....and Srimatri Radharani is the ultimate personification of devotional service and therefore She is the most Dear Most Devotee of all.
(Kadamba Kanana Swami 25/01/2005)