So, that basically means that if a game fulfills the following criteria, it's an RPG:Wikipedia said:A role-playing game (RPG; often roleplaying game) is a game in which the participants assume the roles of fictional characters and collaboratively create or follow stories. Participants determine the actions of their characters based on their characterization, and the actions succeed or fail according to a formal system of rules and guidelines. Within the rules, players can improvise freely; their choices shape the direction and outcome of the games.
- Players assume the role of fictional characters
- Players create or follow stories
- Players determine the actions of their characters based on their characterization
- A formal system of rules and guidelines determine the outcome of those actions
- Players can improvise freely within the rules
- Player choices shape the direction and outcome of the games
What does the Codex think? I personally think it could be polished some more (particularly player skill vs. character skill, improvisation, etc.), but it's a good start nonetheless.