I don't actually have an answer myself yet, there have been a lot of good games that have used choice in wildly different fashions and I can see good arguments for all of the following
--------------------
Alpha Protocol - Can practically choose the fate of every NPC in the game. Boss battles change, become harder, are removed, alliances change, enemies on a level change, each choice isn't presented as good or bad, but just having different meaningful consequences both in terms of money/weapons/enemies and story considerations.
As an example, one rival you can either fight one battle where he runs away and one later on, gain a good reputation with him and do research fight him once when he runs away and then convince him to betray his employer or you can provoke him and make him hate you so that he stays and fights to the death in the first battle.
--------------------
Planescape: Torment - Allows the player to effectively choose the theme of the game and what the ultimate lesson is. Entire game revolves around the concept of choice and change
-------------------
The Walking Dead -
------------------
Mass Effect (Series) - Cross game continuity with choice allowing your decisions to carry across the entire story. Has a lot of downsides, particularly a need to minimise the effect of some choices to save on resources, but the idea was ambitious and compelling all the same
------------------
Heavy Rain - Allowed story to continue even after the death of the protagonists. A fairly large amount of flexibility, a core mechanic of the game and central to the games question of 'How far would you go to save someone you love?'
------------------
KotoR 1 - Poster child for choice in games, using to convey the idea of light/dark side (ish), so very effective in the setting, mainly involved the fate of localised areas allowing you to change them drastically without reducing the scope of the larger narrative. Strong ending
------------------
KotoR 2 - Used choice to push the players philosophical beliefs and to examine a preconceived universe more closely.
-----------------
Katawa Shoujo - By choosing a person to pursue romantically, ensured the player would be much more invested in the relationship and then used this choice (in one storyline) to make the players motivations align with the PCs to create a lesson that the player directly experienced and was directly relevant to them as people. Didn't quite make the final 8 because I haven't played many romance games so I can't tell if the first option is common. And the choices were labelled badly
------------------
-----------------
I'm sure I've made some glaring omissions, but that's what the other option is for! So what game in videogame history has used choice most effectively?
--------------------
Alpha Protocol - Can practically choose the fate of every NPC in the game. Boss battles change, become harder, are removed, alliances change, enemies on a level change, each choice isn't presented as good or bad, but just having different meaningful consequences both in terms of money/weapons/enemies and story considerations.
As an example, one rival you can either fight one battle where he runs away and one later on, gain a good reputation with him and do research fight him once when he runs away and then convince him to betray his employer or you can provoke him and make him hate you so that he stays and fights to the death in the first battle.
--------------------
Planescape: Torment - Allows the player to effectively choose the theme of the game and what the ultimate lesson is. Entire game revolves around the concept of choice and change
-------------------
The Walking Dead -
Uses choice, not to provide player with creativity and a sense of control, but to tie player emotionally to the characters and place the player in situations where they feel the doubt, guilt and responsibility of a situation in a way you couldn't do as a passive viewer
Mass Effect (Series) - Cross game continuity with choice allowing your decisions to carry across the entire story. Has a lot of downsides, particularly a need to minimise the effect of some choices to save on resources, but the idea was ambitious and compelling all the same
------------------
Heavy Rain - Allowed story to continue even after the death of the protagonists. A fairly large amount of flexibility, a core mechanic of the game and central to the games question of 'How far would you go to save someone you love?'
------------------
KotoR 1 - Poster child for choice in games, using to convey the idea of light/dark side (ish), so very effective in the setting, mainly involved the fate of localised areas allowing you to change them drastically without reducing the scope of the larger narrative. Strong ending
------------------
KotoR 2 - Used choice to push the players philosophical beliefs and to examine a preconceived universe more closely.
-----------------
Katawa Shoujo - By choosing a person to pursue romantically, ensured the player would be much more invested in the relationship and then used this choice (in one storyline) to make the players motivations align with the PCs to create a lesson that the player directly experienced and was directly relevant to them as people. Didn't quite make the final 8 because I haven't played many romance games so I can't tell if the first option is common. And the choices were labelled badly
------------------
-----------------
I'm sure I've made some glaring omissions, but that's what the other option is for! So what game in videogame history has used choice most effectively?