An archetypal thing represents an original type after which other, similar things are patterned. With her green skin, black garb, and evil ways, the Wicked Witch of the West is an archetypal villain.
The main characters in Romeo and Juliet are the archetypal "star-crossed lovers" — we often think of them first, and use them as examples. Similarly, Superman, with his chiseled looks, herculean strength, and good conscience, is an archetypal superhero. (Contrast him with Wolverine, whose retracting claws, violent outbursts, and brooding make him an archetypal "anti-hero.")