Brave New Gamer's James Pikover: A post by Ken Feldman of Santa Monica Studios, the developer of God of War 3, stated on the God of War forums that it took their fastest tester 12-13 hours to complete the game. As a game reviewer, I don't consider myself privy to special knowledge or skills, especially considered to testers, who literally play games 8-10 hours a day, and more often 6-7 days a week. But this is a false statement, as I completed the game in roughly 8 hours, 35 minutes, including the end credits and cutscenes.
This screenshot is of my final auto-save.
And for the naysayers, there's nothing wrong with brilliance being 8 hours long. Nothing at all. And that's with fighting every battle and killing every enemy, every time, and with quite a few mistakes. On Normal, as was discussed in the linked thread.