6. "XCOM: Enemy Unknown" (2012, Firaxis Games, for Android, iOS, Linux, OS X, PlayStation 3, PlayStation Vita, Windows and Xbox 360)
You wouldn't think a turn-based game could be so tense. You have all the time in the world to make your next move, and afterward, the enemy can only make one of its own. No sweat, right? In "XCOM: Enemy Unknown," wrong. I don't know what, precisely, made fighting aliens in Firaxis' reimagining of the 1994 classic game so capable of terrorizing players. Maybe it's the distant screams of the humans you're supposed to save. Maybe it's the creepy-crawly sounds the aliens make when they advance on your vulnerable position. Whatever it is, it made a tile-trekking strategy game into an absolute gutcheck. And however you overcome it, whether it's save-scumming (boo!) or soldiering through your losses (yay!), that tension becomes purest exhilaration.