Mars was the Roman god of war (equivalent to Ares in Greek Mythology) and also an agricultural guardian, a combination characteristic of early Rome. He was the most prominent of the military gods worshipped by the Roman legions
Ares the Greek god of war and battle and the instigator of violence, a son of Zeus and Hera. Because of his cruel and war-like nature he was despised by all the gods, even his own father disliked him. Ares could be bloody, merciless, fearful and cowardly and possessed no moral attributes. He was, however, unable to withstand the loveliness of Aphrodite, who subsequently became his consort
Kratos is the hero of Sony's popular "God of War" series, so named because Kratos becomes the (Greek) God of War in the first game after killing Ares in an act of revenge for tricking Kratos into murdering his wife and daughter before any of the games took place. His fight with Ares in the first game isn't the only feud Kratos gets into, as his father Zeus tricks him into abandoning his godly powers at the beginning of God of War II. Kratos's life sure is messed up!