Making a compelling synopsis for your game

I've been going over how I'm going to do the synopsis for my game and am very uncertain about one area; the story. How do you get your prospective players interested in what the story of your game is about, when you don't want to reveal the story elements that are what make it interesting? Do people just mention the gameplay elements and setting? Mention the characters? Keep the story elements vague? I'm really having a hard time thinking up how to mention any of the story elements without making them sound incredibly generic, but revealing what makes them not generic would ruin their reveal in the game. How do other people approach this?

Here is something I wrote a while back in a reply to someone who was asking how to avoid giving too much away and so giving a spoiler.  Maybe it will spark off an idea for you.  The example I give is purely made up, and had nothing to do with the poster's own story.

 ...However, perhaps something along these lines

"The story opens in a small, wooded glade, closed in, claustrophobic even, but will open out into a huge world where [name of character] must face questions s/he didn't even know existed.  Finding the answers will mean traveling to strange places, a journey which will change him/her from a shy academic into someone whose actions and choices will have consequences that are literally life changing.  If s/he had known this at the beginning, would the journey even have begun?

Why did the Mountain Mage disappear?  Who is the man they keep seeing in the distance?  What is the meaning of the book that no one can read?  As a small group gathers around [character] these questions seem to provoke a sinister response.  They sense danger, but cannot see its source.

etc."

Gives a flavour, without actually telling you what happens.

I don't know if this can help, but I always try to put myself in like I'm the player, how is my respond or am I excited maybe with the game story if I'm the player?
For example, I play a new game that I never played before, than if after a while I played the game and I feel excited, then the game is succed, thus I will try to study how and when I become excited by that game, the story, the battle, or what, after that I try to implement it in my game. Of course I still keep my own game element. But I'm the person who believe that story is the main element of the game, so if your story is great then the player usually will interested to find something more about the game. So I like to keep the main story a bit vague, and maybe twist it in the middle or later game. Example, in the very first start I introduce a bad guy that perhaps he is the man who will make the world destroyed, but in the middle game, the plot began to change, like the bad guy is actually not the real bad guy(perhaps he is a good guy instead), and there's more than the eyes could see, the main character friends is the real bad guy. That just example.

For me actually I don't really care if the player will excited with my game or not, I think if I myself is excited with my own game which is almost impossible(how come I excited with a game that I have already know it's story plot?) then other peoples have great chance to excited. Simple like that.

I write my description in a way you would find on the back of the box, or like in a manual. It describes briefly what happens in the first 15 minutes of the game, introducing the main party, their goals and the bad guy. It ends in a way that (hopefully) leaves the player wondering where the story is going beyond that.

Then I also have a section that gives a short description of each party member that you'll see within the first 15 minutes of the game (not revealing any future party members) and the 'main' bad guy (pretending it's the main BG, while the real BG shows up later in the game, lol).

That way your players know what to expect when starting up your game, while still getting plenty of surprises later on.

First and foremost, remember to keep it short and concise. Nobody will be reading a wall of text, unless they're really patient or already have an interest in the game prior to reading this synopsis. 2 or 3 paragraphs should be reasonable enough, in my opinion.

In the first paragraph I tend to give a very brief summary as to what the setting is like. Don't go into huge amounts of details. Just mention a few points that makes your game's setting unique. Is it a distant future where robots have taken over? Is it a medieval fantasy where mages are being hunted down? Is it a horror story where the main character has no clue where he is? And so on. And whilst introducing the setting, ease into the main plot. As the others have pointed out above, just mention the story events that would've happened in the first few minutes of the game (by this stage of the game you've hopefully have introduced the main protagonist, the main conflict, and possibly even one of the villains).

The second part of the synopsis is creating the hook. Ksjp 17 did a good example there with the questions being asked closer to the end of the synopsis. By presenting these questions about certain plot elements that get revealed early, you're hoping to create a hook that will get the potential players interested.

Hope this helps.

That's actually really helpful advice from all of you and I'm going to make use of it. This one is proving a little difficult for me because my game throws a pretty big curve ball right near the start that's central to the main conflict, and alas I realize I really can hardly make any mention of it beyond the vaguest of questions without spoiling it, so I will use some of these techniques to emphasize and build up the other elements and setting and think that should do the trick.