If we assume that God and Devil exist, then look at what both of them have given to us:

God: Life (bound to death), free will (and the judgement of its usage), shape (an error-prone one), commandments, Heaven (comes with Hell), war, prejudice, suppression of minorities, genocide, slavery, abuse of authority
Satan: Knowledge of good and bad, skepticism, questioning of authorities
(Source: Bible)

Tell me more how Satan is the bad guy int his whole scheme.