Anand has a nice post at his site on how Greek and Hindu deities are so similar. He also looks at the spread of Hindu myths across Asia. The wider point is that the similarities between the various mythologies don’t stop with Greece and India. Norse mythology is remarkably similar. For one, Thor is the king with the thunderbolt as his weapon of choice.Take a gander at Zoroastrianism, where you have gods such as Mithra and Varuna, although in their mythology, the ahuras (asuras) are the winners of the cosmic battle.
A comment on Anand’s post remarks on the fact that we humans worship nature gods in human form. In a sense this anthropomorphic act – man has created God in his image rather than the other way around – has been debated in Indian philosophy. Adi Sankara, who propagated Vedantic thinking encouraged the worship of a personal god only to the extent that it allowed one to channel ones bhakti (devotion) better. Sankara is at pains to point out that the reality (Brahman) is unknowable using the senses and intellect alone.