Sri Chaitanya Mahaprabhu has advised us to engage in one-pointed exclusive unmotivated devotion to Sri Krishna. You will find evidence in the fourth verse of Shikshastaka written by Him. The Highest Sweet Form of the Supreme Lord - Nandanandan Sri Krishna, appears in this universe only once in one day of Brahma. Finite human beings cannot calculate the span of life of a day of Brahma. The span of life of fourteen Manus is equal to one day of Brahma. Nandanandan Krishna has appeared in the 28th chaturyuga of Vaivasvata Manvantara (7th Manvantara) in the Dvapara yuga. Nandanandan Krishna performs sweet pastimes only with His own personal associates in the above mentioned special Dvapara yuga. But just after that Dwapara yuga, in the same Manvantara, in the next Kali yuga, by taking the complexion and mode of worship of Radharani, Nandanandan Krishna appears as Gauranga Mahaprabhu to distribute the highest Krishna-prem to all, irrespective of caste, creed and religion, even to beasts and birds, without consideration. So, He is the Most Munificent Form of Godhead. You are to go through the verse of Vidagdha-madhav written by Srila Rupa Goswami:-

anarpita-carim cirat karunayavatirnah kalau
samarpayitum unnatojjvala- rasam sva-bhakti-sriyam
harih purata-sundara- dyuti-kadamba- sandipitah
sada hridaya-kandare sphuratu vah saci-nandanah

Here the words `anarpita-carim cirat' mean that the highest Krishna-prem was not given for a long period. We are very fortunate that we have got our birth in this very Kali yuga and close to the appearance time of Gauranga Mahaprabhu. All sweet delightful relations have been manifested only in Nandanandan Sri Krishna. Actual relations of master and servant, bosom friendship, parental affection, consorthood of love, all kinds of delightful relations exist only with Him.