16. [...]While most of the demigods owed their existence to Zeus, she was the only woman of whom he condescended to be called the father. While he took most interest in the son of Alcmene and the children of Leda, he so far showed preference for Helen over Heracles, that, having granted such strength to the latter that he was enabled to overcome all by force, he allotted to Helen the gift of beauty, which is destined to bring even strength into subjection to it. 17. Knowing, further, that distinction and renown arise, not from peace, but from wars and combats, and wishing not only to exalt their bodies to heaven, but to bestow upon them an everlasting remembrance, he ordained a life of toil and danger for the one, while he granted to the other beauty that was universally admired and became the object of universal contention.
Basically, he says, Zeus gave Helen the ABSOLUTE most powerful gift, raising her up over Heracles, because even strength is helpless in the face of such beauty as Helen possessed. And not only that! But as further proof of his favor, he made sure Helen would NEVER be forgotten, because, basically, she would be fought over forever by everyone.
But the thing Isocrates fails to take into consideration is this: Heracles can choose where to leverage his strength. He can decide to ransack a city, or kill a lion with nothing but a club and his bare hands. He has CONTROL over his strengths, for the most part -- unless he's being directly manipulated by the gods, or else has flown into a rage (possibly because of direct manipulation by the gods.)
Helen, on the other hand, is given this incredible gift, this incredible beauty, but left with no control over it. None. And to add insult to injury, she is BLAMED and held solely accountable for the results. She is cursed for causing the Trojan War, cursed for betraying and abandoning her husband and daughter. All the blood of all the men who follow her to Troy, and all the men who fight for her right to remain there is on her hands, all that death on her head, and her head alone.
Yes, Helen was remembered. But not as a hero. Unlike Odysseus, and Heracles, and Theseus, Helen is not famous for her noble deeds.
She is infamous for her lack of virtue.
If that's how Zeus treats his favorites, I'd rather be overlooked altogether.