Firstly, it's all about presentation: detail helps, but too much can be daunting. Show a good plot with some idea of depth. A good backstory always helps.
If it's a rule based game, try to be as clear about the game rules as possible, rather than copy/paste "Normal SC rules apply". Try to keep rules and background SPERATE (It's why there are two pages...)
Try to avoid having the SC as a main party character. A Plot Vital NPC is fine... but if they're the central hero, tends to take the focus off the players.
Give players details, as much as possible without confusing them (Ensuring continuity) so that they can make a good character (Good detail and depth tends to attract the better class of writer...)
DON'T get disheartened if your game only gets 1 app in three days. Sometimes players have a "wait and see" attitude: many large stories are made then just crumble after an hour! So, maybe throw updates, some background "story" examples, and you'll draw in people.
Arguably, however, no "formula" is a winning one. Some simple games get tonnes of players, just via the concept. Some really well thought out and complex games get maybe 2... And some just don't take off. You need something that seperates it from other games and acts as a hook.
Well, enough of my vanilla advice. Hope this is sueful, but I'm always happy to engage in a discussion about what works and what sometimes doesn't

LOTS of good and bad experience on my end (As a good and bad admin...)