Triangularity In Game Design
Schell describes a type of choice in game that is high-risk / high-reward. For example, choosing to shoot the space ship in Space Invaders or taking the short cut in Mario Kart. Schell goes as far to say that 80% of the time if a game isn't fun, it's because it's lacking these kinds of choices.
References:
- The Art of Game Design - A Book of Lenses (2nd Edition) (Chapter 13. Game Mechanics Must Be In Balance)