Viking: Battle for Asgard is not a terrible game. There may be a good game in there somewhere, but it falls into a standard hack-and-slash rut of boring and uninspired gameplay that leaves you wanting more from the experience. Norse mythology is such a rich setting that if the game had been done well, it could have been incredible and boasted a terrific story, characters and gameplay.
Unfortunately, Viking never quite achieves this, leaving you with a pretty mediocre action title that's hard to recommend to anyone, except those who really enjoy shallow action games.