All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.
The hadeeth, as you mentioned, was reported by Al-Bukhaari, and he entitled it: Chapter: The Lord Speaking to the People of Paradise.
Ibn Hajar said, "What is meant by the saying 'nothing makes you satisfied' is the human being and his innate nature, as he always asks for more, except those whom Allah wills."
Ibn Battaal said in his commentary on Saheeh Al-Bukhaari, "His saying 'nothing makes you satisfied' is dispraise of not being content with what he had and asking for more; i.e. your eyes and self are not satisfied with anything."
However, Ibn Hubayrah said in Al-Ifsaah, "The saying of Allah Almighty 'Here you are, O son of Adam, nothing makes you satisfied!'; the way I understand it is like teaching him to not be satisfied, and what is meant is that he should not be satisfied with the favor (of Allah) and should not stop asking for more, and it does not mean, as people may have understood it, rebuking him for asking for more."
Allah knows best.