perry_blueberry said:
I think there is a distinction there when comparing games to other art forms.

There is also a distinction when considering that this question was asked by an aspiring writer, in the Writing forum. Not all games need story, but some types of game depend on story entirely. Since @yanry ‘s goal is “a story game” (he said “a story for a game” which to me implies a story-based game*) you’d start first with the story, then determine the mechanic (which implies genre) that best tells that story.

*You can slap a story on a chess game or a football/soccer game, but what for? (Note that people have slapped stories on all sorts of games that didn't need stories.)

perry_blueberry said:
… I tried to make a few games where I started out with some story/situation and then I tried to slap on the mechanics after the fact. It just didn't work for me that way because I kept coming back to “so I have this interesting story that the player can unravel as the game progresses but what the hell are they going to actually be doing and why would they stick around long enough to unravel the story?

I would suggest that in such a case, it might be worth looking in particular at those genres built around a story-centric approach: I daresay that not much mechanical investigation is necessarily called for if one chooses to make a point-and-click adventure or a visual novel, for example.

(Note that even those genres can bear new mechanics, I do daresay. However, if one is primarily interested in the story, and the story doesn't seem to call for additional mechanics, then they pretty much have a set of mechanics in place already.)

perry_blueberry said:
I've seen some games, like Firewatch and Telltale games, where the mechanics aren't all that impressive …

Thinking of Firewatch in particular, I don't think that I'd call its mechanics unimpressive at all. Indeed, its use of exploration, discovery, and dialogue mechanics to support and guide its story were pretty cool, I do think!

I'm less impressed by the TellTale games, myself--but conversely, I have the impression that there were those who liked them.

Perhaps more impressive to my mind in the TellTale vein might be Until Dawn, which I felt made pretty good use of its choices--and even of its quick-time events, as much as I dislike those.

perry_blueberry said:
Obviously there is no right answer to which one is better but most commercial successess are outlined to some degree.

To what degree, however?

After all, outlining is a continuum, not a binary: I doubt that there are many authors who exclusively work without one, or who exclusively and unbendingly rely on one. So, indeed, I daresay that most successes are outlined to some degree--because I doubt that many stories, successful or not, eschew it absolutely.

Thaumaturge said:
I'm less impressed by the TellTale games, myself--but conversely, I have the impression that there were those who liked them.

I liked them. Other story games I liked were Myst and Everybody's Gone To the Rapture, and Beyond Two Souls.

Tom Sloper said:
I liked them. Other story games I liked were Myst and Everybody's Gone To the Rapture, and Beyond Two Souls.

That's fair! ^_^

(And I very much liked the Myst games myself, and did quite like the non-linear approach used in Beyond. The other I haven't played nor seen much of, I think, although I know of it.)

Personally, I don't often sit down and “make a game” in my head, it'll just be happening when I play an existing game and get an idea for something related but in a different direction, or just randomly throughout the day with various stimulus. I have heaps of different ideas ready to go, and I keep adding more to the pile.

But if you look up game jams, they have to make up new game ideas very quickly using only a few words as stimulus. Some big hit indie games have often come out of that, like Don't Starve.

On that note, one of my favourite ways of inspiring game ideas like that is this game name generator, created by “Tom Hall”, the same guy that was level creator for the original Doom in id Software. https://thattomhall.itch.io/rndgame​​

More often than not, games ideas are invented around something the player does or experiences, rather than a story, and the story is created around that game idea. This might not entice you as much if you're more into story writing, since the methods above may not excite you if you're not looking to make a prototype of the game right away. They might seem silly, or trite, from a story writing perspective.

Domarius said:
This might not entice you as much if you're more into story writing, since the methods above may not excite you if you're not looking to make a prototype of the game right away. They might seem silly, or trite, from a story writing perspective.

In all fairness, similar methods are sometimes used for story-writing, too: coming up with a plot from a simple prompt is a not-uncommon exercise, I believe.

For two examples, I've seen a “write a plot from this title” thread in a writers' sub-forum, and I know someone on Twitter who used to put out “story dice” prompts for people to write around, as I recall.