According to Mechademia (vol1 p148) Mononoke and Sun were based off similar folklore. For Mononoke it was "the story of Yamato Takeru, a legendary trickster who almost died in the mountains of Japan when, after offending the god of the mountain by accidentally killing a deer, he was attacked by a boar or a snake (accounts differ) and poisoned. A white dog that led him to a healing spring saved him."
For Sun it was "the story of the Aeonia-kamui, the sacred ancestor of the Ainu, who was first warned away from danger by the younger sister of the wolf god" when she turned into a dog and scared him off, and then when he was injured she "transformed again into a beautiful woman. She asked him to marry her, but he ignored her. Undeterred, she followed Aeonia-kamui home. Some legends say that the Ainu people were born of that union of human and wolf."
Finally "the similarities between these two stories suggest some common origin, or perhaps just later influence".
As for me, my favourites are Nausicaa and Mononoke, although I haven't seen Porco Rosso, Kiki, Totoro and a bunch of others.