Telemachus could also be counted as a hero in The Odyssey. He stands up to the suitors, men who are quite contented to exploit the rules concerning hospitality and plot Telemachus's death. He is also brave enough to sail out, away from home, to go in search of news of his father, Odysseus. The dutiful son who helps to avenge the wrongs done to his father is very much a hero to the ancient Greeks—Orestes, the son of Agamemnon who slays his mother and her lover after they killed his father, is also revered as a hero.
It's true that Athena helps Telemachus quite a bit, but she—and other gods—help his father, too, and that doesn't make him any less of a hero. In fact, the gods often do not help individuals they find unworthy, so the favor Telemachus finds with Athena is really to his credit. Then, once Odysseus returns to Ithaca, Telemachus bravely assists him in slaying the suitors and reclaiming his rightful place. For these reasons, Telemachus can be seen as a hero as well.