Today is about how Poseidon represents the values of his Pantheon and cultural origins. This one is relatively easy for me as the virtues that Poseidon values are closely in step with those of the remainder of the Hellenic Theoi. He values excellence in endeavor (Arête), hospitality (Philoxenia), piety, and the grace (Kharis) of reciprocity between mortals and the Theoi.
As the values of Hellenic culture have remained mainly the same from before the classical period to the modern era, and these values are mirrored in the stories about the Theoi; it can be assumed that Poseidon resembles those values as well.
Greece was and is a culture based largely on the interaction of land and sea. This interaction is part of what formed the values of Hellas, the Hellenic Theoi in general, and Poseidon in particular.