I play and run RPGs as reality puzzle games. I like them because they have the same payoff as other pattern finding games, those with win/loss conditions and lots of analysis like Chess. It's fun for me when memory, insight, and intelligence matter in the performance of a game. And being pushed to remember what has, is, and may happen in an imaginary world flexes my mental muscles, while immersing me within it.
Not to mention all the great skills RPGs improve in players: defining and achieving goals, planning/prioritization including having a plan B, C, D, etc., teamwork and organization, communicating clearly and improving vocabulary, note taking, journal keeping, inventorying, and mapping, time management and scheduling, observation skills like being detail oriented, while retaining the big picture, critical and creative problem solving, high concentration and focus, quick thinking, learning when to go it alone rather than with the team, self-restraint, maintaining a working memory, emotional control, proactive task initiation, personal flexibility, and stress tolerance.
I'm sure there are more, but the rules/code I use behind the screen is geared towards pushing players in the above.