There aint none. Not really. What you have are skirmish miniature games where the participants can play roles if they wish,but playing roles aren't necessary.
Pretending to be someone else doesn't have to involve killing things and taking their stuff. You don't even have to succeed at anything, for often the mark of an individual involves how he handles failure. And very often your opponent's success can mean success for you.
As a Game
Now RPGs aren't impossible, just dang difficult. It isn't goals you need to achieve, but a measure of how well you played your role. At no time can that ever be objective, for playing roles is a subjective thing, and judging how they are played is perforce subjective as well.
Nor can such an effort ever be balanced, for even a small world is going to be complex, sometimes complicated, and they shall always be that which is better or less than you. Just remember, where a dragon may slay a kobold, a swarm of kobolds will always boss a dragon around.
I'd druther treat them as guides. Guides to living a life in an imaginary setting. While they're not really happening, you can treat them as if they were happening. For nothing has to be real in order for us to treat it as real.
So I'll be writing about adventure guides in this blog; guides to adventure in which the mechanics of how a world works are presented, and advice on how to handle adventures in an imaginary world.