This is a rather philosophical question.

Suppose we travel the galaxy and meet a species like the Q from Star Trek. They are seemingly omni powerful and have bascially all the characteristics we would give a god. But the question is, are they gods?

Or more generally speaking: How do we differentiate a very powerful beeing from god? I mean however we meet might or not be a god described in earth´s mythology. How would one be able to identify them?