I'm not sure if this falls under writing or game desing, but I think mainly writing. So, I'm working on a game and I've got the code to the point where I am starting to think about gameplay and plot. I have some ideas but have run into an issue. There are certain moments in traditional storytelling where characters have to make difficult choices. These are generally very compelling moments. They mainly seem to serve two purposes. The first is to reveal an aspect of the character's personality. The second is to change the character's environment and cause their lives to change in some way. I want some of these moments in my game. The easy way to do this would be to script them, but that isn't good enough. I want the NPCs to make these decisions based on what has happened previously in the game. I also want the player to be able to make some of these decisions. Making this happen and having the world react intelligently isn't easy, but it can be done. The problem is replayability. Part of what makes these moments so compelling is that once you have seen, heard or read what happens, it can never be changed. No matter how often you re-read/re-listen/re-watch the story, the character will always make the same decision. In a game this isn't true. Even if we came up with a convoluted save system that doesn't allow the player to go back to before this moment they could replay the game. Even if we make it so hard to change what happens that the player will never do so, the simple possibility that they could seems to take away some of the power of these moments. Is there any way to overcome this or is it a limit of the medium? Could we create equally powerful stories by showing the consequences of all of a player's possible choices even though we have to sacrifice these powerful moments?

Yes.
People usually try to avoid emotions they don't really like and that also might make the story weaker.
And if we compare the games with linear story and games with non-linear story, the linear stories are always more powerful. That's true because choices in games are nothing more than pointless experiments to players. They don't have powerful consequences, and if they make gameplay worse, the game won't be played anymore. The player has the chance to quit playing at any time so I support making linear stories and therefore making the playing experience more powerful, more unique, better.

So you have a choice here - basically equal choices or a weak story.

P.S. The only good choice I had to make in a game was in Splinter Cell: Pandora Tomorrow - the Jerusalem mission - to kill or not to kill the other agent. I think it was one of the best choices ever implemented in a game. It didn't have the power to change my mood, it only changed the dialogues and gameplay at the end of the level.

Is this an RPG? RPGs are just not replayable, there's no point worrying about replayability unless you want to plan for one specific 2nd playthrough in which new areas and/or abilities will be accessible and the story will diverge in a specific major way from the first playthrough. It would be a pretty good idea to design a first playthrough that is hard-won through sacrifice, then a second playthrough where all the sacrifice is avoided for a perfect happy ending.

But, I think it's quite misleading to start out talking about choice if you're talking about a situation where the player does not actually get to decide anything and can't have any effect on the plot direction. Fake choices tend to piss off players and thus are usually not given to the PC to make. If you really want to focus on hard choices, give the choice to an important NPC to make unless you are going to let the player actually make it.

But to some players including me, the perfect happy ending is the most desirable and thus the most interesting. (It's only interesting if you've done a good job of creating lovable characters though.)

Does having more possible defining moments make each of the defining moment weaker?
Re: Tim

I think that was your question. You do not have a problem implementing non-linear game story. You don't have a problem letting the player save the game and replay. You are asking whether simply letting the player know that there are alternate endings would make the defining moments of the story weaker.

I don't think it would dampen it just because you have multiple defining moments in different paths. You should just focus on making each of the defining moment strong, so that each path has momentum to carry the plot forward.

Thanks for the replies. It isn't an RPG I'm not sure what genre it would fall into, but the main emphasis is dialogue, with a bit of shooting for good measure. I'm planning on keeping it to a couple of hours so that I stand a chance of actually getting it done, so replays are a possibility, but thats not really what I'm trying to get at. The choices the player makes will affect the outcome (I hope). The player can't influence where the plot goes and I'm not trying to make them think that they can. The decisions they make should influence which characters survive to the end and what their relationship with the player is. Wai was fairly close to what I'm trying to deal with.

To take an example from Mass Effect (SPOILERS) the moment when the player has to choose who lives between Ashley and Kaiden should be incredibly powerful. If done well it would have the viewer on the edge of their seat in a film/tv show. When playing the game I knew that if I wanted to I could re-play the game and so I didn't care that much. I'm not likely to play through again just to change who survives, but the fact that I could is enough to ruin the effect for me.

Having thought about that I'm now wondering if unique characters would help. If Kaiden and Ashley were completely different every time you play the game, then chosing which one dies is meaningfull because you will never experience the game with that exact character.

That would present its own problems though. How to create a character generation system that can make characters unique enough to be individual but similar enough to fulfill the plot functions they need? How to explain to the player that once they decide they will never see that exact character again? Would this be frustrating, knowing that that character will never come back?

How about delaying the point of effect with respect to the point of choice; or obscuring the relation between the two?

For example, you could let the player choose before reaching chapter 4, and the full effect of the accumuated choices is not observed until chapter 5. By the time the player realizes that the choices matter, the player would have complete so much and want not to start over. The player might not know how he needs to play differently to get a different ending, the relation is obscured.

The problem with that is that it is the consequences of the choice that make it powerful. If you don't know what the consequences are then how can you care what decision you make?

As you don't know the consequences, choice is only perceived as a harmless experiment which can only frustrate the player later because he can never know the whole story as he is actually not the character he controls. So, if you want a choice in your game, let it be a "weak" choice or... maybe you could try to display the thoughts of the character that the player controls and give a short summary of his opinion about consequences. But that opinion must be clear, not some kind of "invisible text", otherwise it will not work because gamers are usually not good thinkers.