SB 12.13.16
nimna-ganam yatha ganga
devanam acyuto yatha
vaisnavanam yatha sambhuh
purananam idam tatha
Translation:
Just as the Ganga is the greatest of all rivers, Lord Acyuta the supreme among deities and Lord Sambhu [Siva] the greatest of Vaisnavas, so Srimad-Bhagavatam is the greatest of all Puranas.