That both the Gilgamesh Epic and the Odyssey deal with the episodic wanderings of a hero, would not be sufficiently specific to establish a genuine relation between them. But when both epics begin with the declaration that the hero gained experience from his wide wanderings, and end with his homecoming, a relationship dimly appears.... when we note that whole episodes are in essential agreement, we are on firmer ground. For instance, both Gilgamesh and Odysseus reject a goddess's proposal for marriage; and each of the heroes interviews his dead companion in Hades.
Introduction - The Common Background of Greek and Hebrew Civilizations (1965 [1962])