Who was considered judaism’s greatest prophet?

Moses is considered Judaism's greatest prophet. Although it is true that unlike Islam or Christianity, there are not any specific prophets that is considered the supreme of the religion of Judaism, but still Moses has been considered one of the greatest prophets of Judaism.  Moses is considered the greatest because he was the prophet that directly communicated with God. This power was a rare power and this is the reason behind thinking Moses as the greatest prophet regarding the religion of Judaism.

You're asking an opinion question, so it's possible that you'll get
different answers from different people.

However, one of Maimonides' Thirteen Principles of Faith is the
primacy of Moses among the prophets. 

As an example, one of the verses of the "Yigdal" hymn of the
Hebrew prayer service ... a poetic summation of those principles ...
says "There has not arisen in Israel another so perceptive a prophet
as Moses."

(Sorry if the translation is awkward; it's my translation.)

It is c. naturally in the environment