For passionate aspiring game designers, that’s a huge question. The medium has so much potential for complex storytelling, the ideas behind a game that even comes close to that potential require volumes of descriptions.
However, the general design for a truly enriching game would be focused around character community within the game. An example of a game that moves in this direction is Red Dead Redemption. With its complex cinematic storytelling it develops characters that you then see interact with each other and can yourself interact with to some degree, though the repetitive violence throughout the game hinders this aspect, I think. Too many “serious” games focus too much on single, usually empty characters. The copout for these spiritless designers is that the main character is supposed to be the player, therefore needs no personality of its own. It’s pathetic.
It doesn’t matter how many elaborate game mechanics are shoved into games, until developers learn to devote their creations to the principles of storytelling, games will never reach anywhere near their potential.
Heavy Rain is a great example of what the future of complex games may look like, it is basically an interactive movie where you, the player, effect the point-of-view and flow of plot. This allows you to become “one” with the characters, through more than spectator but through interaction—through effort. Demanding skill is not the point—demand effort from your players. That is what connects them to the story. The character’s effort becomes the player’s effort, thus opening up beautiful unconscious sympathies allowing the story to flow through the the players exposed soul! This is something that can not be achieved by the general audience in movies and books—it forces participation that only a minority achieve with less interactive mediums.
These are more principals for game design than what you would normally call ideas. My ideas for specific games I keep until they are developed into something that can be effectively shared. It’s not that I do not want to share them, it’s that I must keep them in my world before they enter the harsh real world. It’s a psychological thing. Besides, basic ideas are easy to come up with; it’s developing them into practices that people need help with.