Sub Optimal Quest Results:

If the options are winning or failing a mission, and the game is about winning missions, then obviously people will want to win the missions, rather than get varying degrees of failure (though if the relative reward for winning vs. failing is small enough they may not bother replaying). Similarly if there are "right" and "wrong" dialogue options, people will want to pick the right ones.

If you want multiple outcomes, you could instead try to make people choose between one interesting possibility and other interesting possibilities, as opposed to simply more or less correct or rewarding possibilities along a linear scale. In the murder example, you could have the murder be a "justifiable homicide" of some kind, and finding the killer and putting them away (or maybe even killing them if there is a death penalty) may not be the 100% doubleplus morally superior choice.

And if that is too impractical, you could just add another variable to balance the negativity of failing. There could be some mobster that pays the police force good money for failing to solve crimes, so your option #1 would get you no conviction, but lots of cash, and vice versa for #5. That's obviously just a crap example though (although it could add some interesting choices of which cases to drop, if the player really needed the cash), but another could be that the mobsters get angry at you for solving crimes, and give you a "wanted level" like in GTA. And so forth.

I feel that you almost can't add enough variety in this respect, and I'm a bit disappointed at the lack of it. There are basically two groups of games I see here: mission oriented (RTS, FPS, etc.) and progression oriented (MMOs).

In progression oriented games, most players are at the very least going to want to be given a second chance at pulling off a quest, especially if it gives them loot. In WoW, failing a quest permanently would be a big deal, as you'd lose out on a fair amount of XP, money and gear. Having multiple levels of success sounds like a good idea here though, especially if you can retry it to get a better result (although you'd have to be careful to not reward too much repeatedly, or people will farm the quests). Anyway, I fully support the idea of a quest that does something of this sort:

Defend the town against the incoming undead:

Basic goal: Survive
Optional goal: Protect townsfolk
Optional goal: Kill the necromancer leading them

In this setup, every person who survives gives a small bonus to xp or something, and killing the necromancer might give you new loot and bonus xp.



In mission oriented games, I'd like to see more games where failure is an option. I can't think of a game in recent memory where you were allowed to fail and keep going. In Command and Conquer, Warcraft III, Starcraft, and so on, you either win the mission or you try again. Real wars involved lots of wins and losses on both sides, I'd like to see a branching campaign where you can experience what happens when you don't win every battle. The obvious downside is that some battles you have to win or else (i.e. your commander is killed, the nuke is launched at your main base, etc.), and the game gets much more complicated in a hurry.

Still, I don't think I've ever complained that a developer put too much time into the story.

Some thoughts for this specific example. If you want to encourage 1 or 2 you could make it so that you can either pursue the lead to the next clue or protect the next victim. Ex: the either go to the suspects apartment and look for clues or go to the site where you think the killer placed a bomb. If you go to the apartment people die; if you go for the bomb site you give the killer enough time to sanitize the apartment of some or all the clues. An alternate form includes setting the building on fire: either get the clues or evacuate the building.

If you want to encourage 3 you can make the player want to finger the wrong suspect. This can be a bribe, to remove from power someone who gets in the player's way, or just an utter jerkass. Ex: the false suspect is a by the book officer of some sort who won't bend the rules enough for the players to get a good item later. Another example: suspect is a child molester or a war criminal who got off on a technicality. Or you can make 3 really easy by having a false confession available (bonus points for mind altering the guy so that he really believes he committed the act). You can also give the player a weird reputation for trying to find the real killer under those circumstances, like if trying to find the real killer looks like pursuing a vendetta. Or there's making the false suspect a cop killer: try to find the real killer and the cops might starting giving you a hard time because they think you're trying to protect a cop killer.

Alternately, you can discourage 4 by making it so that the player has to do some questionable or resource consuming tasks in order to get it. Example: killer is a psychic in a world where people don't believe in psychic phenomenon, so ensuring a conviction may involve bribes and planting evidence. Alternately, the only way to find the killer is to do something that isn't admissible in court, like using your own psychic powers or beating the suspects girlfriend until she admits that the alibi she supplied was false, again requiring some sort of bribe or planting of evidence. Or you can discourage 4 by making the real killer one of your allies. Or you can royally piss off one of your allies by finding the right killer (ex: the killer was his son). Then there's making the rules of society especially oppressive so that the punishment outweighs the crime. Or there's making the killer the last living descendant of the great magician who sealed the plague away and whose blood carries the spell that keeps it from returning. If he gets the death penalty then suddenly everywhere you go people are dying from disease; stick him in prison and the same deal happens twenty years later because he doesn't breed (if you really want a crapsack world, make it clear in the epilogue that if you let him go the only reason he does end up breeding is because he became a rapist). Then there's making the culprit someone you need later: if you convict him, he won't testify later against the mob boss. Or you can make the killer genuinely repentant and he's gone off to the third world and spends his life fighting disease and feeding orphans or will later betray the big bad for crossing the moral event horizon. Or the killer isn't the most competent lieutenant of the big bad, and if you let him go you'll get an easier fight later.