I tried to remember how was Ares when he met Xena and how he was in 6 season. Ares was changed by Xena! His love for her became the reason why the God Of War became the God Of Love...And i am sure that Xena had powerfull feelings for him because she had the ability and the opportunity to kill him but she didn't. Ares gave him immortality to save Gabrielle's and Eve's life. But he didn't do this to save them, but not to hurt Xena. The old Ares never could do this. So the love is so powerfull to change Xena and after to change Ares!