> Procedural generation helps here. A good few long-lived free software games (notably Nethack and Oolite) have mostly or entirely procedurally-generated content, and lots of flexibility. That way, merely knowing what can happen isn't going to spoil the gameplay, because you never know when the game will choose to hit you with what, or in what combinations.
Do you think that could also be applied to e.g. arcade or platform style games? It seems to me that it is only suitable for certain categories, but perhaps that is just my lack of imagination.