My bigger problem with the series is just how it takes a small snippet out of the whole manga. Now, if that snippet had made sense I wouldn't have complained. But the first episode shows him in the future with all the battle damage he's taken fighting demons. Now flash back like 20 years and let's have a nice, totally non-magical medieval story about ambition and battle with a random Zodd thrown in there. Oh, look, here's the end; everybody's eaten by demons, have a nice day.
It seems like they should have either played up the magical aspect so that you had a sense of demons coming, or just simply ignored it and changed the ending (yes, I know the manga fans would have howled), but doing it halfway made the anime feel like it had multiple personality disorder. My vote is personally for the latter; at least from the view of somebody who's only seen the anime, it would have easily stood on its own without the supernatural aspects.