Currently among the highest-grossing apps in the Apple App Store, the sword-slashing fight game “Infinity Blade” is one of the must-have games of the year. Like “Angry Birds,” it’s surprisingly addictive. I’m far from a hard-core gamer, but I can recognize a masterpiece when I see one. Odds are, you’ll enjoy this one, too — with a few caveats, of course. First, you should enjoy challenges, particularly those that involve slashing, slicing, magic and armor. Second, you should appreciate amazing graphics.