Krsna left Vrndavana. All the gopis, they passed their days simply crying for Krsna, but never condemned Krsna. Whenever somebody came… Krsna also was thinking of them because gopis are the greatest devotees, topmost devotees. There is no comparison with the devotion of the gopis. Therefore Krsna was always obliged to them. Krsna said to the gopis that "You have to be satisfied with your own business. I cannot return you anything for your love." Krsna, the Supreme, the all-powerful, He was unable to repay the debts for the gopis. Caitanya Mahaprabhu said, ramya kacid upasana vraja-vadhu-vargena ya kalpita. There is no more better worship than what was conceived by the gopis. So gopis are the topmost devotees. And amongst the gopis, Srimati Radharani is the topmost. Therefore Srimati Radharani is greater than Krsna.
From Srila Prabhupada's lecture on Bhagavad-gita 2.3 — London, August 4, 1973