Alternate Rule 2: To be a sport, an activity must define its success objectively rather than subjectively. This requires some clarification, because there is a lot of subjectivity in all sports. Did the runner touch home plate, or not? Did the sprinter beat his competitor by a few thousandths of a second, or lose by that same margin? You could argue that all attempted judgments of these types of close calls are subjective.
However, the crucial distinction is that, whether or not our judges, umps and referees can always find it, there IS an objective answer to these questions. The athlete DID touch home plate, and if he's called out, that's a regrettable error. The runner DID win the race, even if it's too close for us to tell accurately. The subjectivity is in the judging, not in the actual sport. The only place you find subjectivity in sports is in some of the more loosely defined rules--did he make a "football move," did the batter attempt to get out of the way of the pitch, etc. Overall, these sports are objective, with some subjectivity thrown in.
That leaves out, once again, figure skating and gymnastics--even under this new rule, they still don't make the cut. These are performances, much more similar to ballet than they are to, say, soccer. The key factor that makes them performances and not sports is the fact that their success is defined subjectively--hence, the creation of this new rule.
So, another option for my fellow sports-definers out there. Maybe this one will be a little bit more popular.