The Oxford Dictionary says that sport is "an activity involving physical exertion and skill in which an individual or team competes against another or others for entertainment." Video games certainly do involve physical exertion. It's usually not as much as in soccer, for example, but it is there. How can you draw the like? Is golf a sports? Is darts a sport? Archery? The most involve standing in one place and launching something away from you. You could say that they don't involved that much physical exertion. They certainly do involve it though and they are sports. I like to qualify videos games as cybersports, when they are play on a high competitive level.