I am really a huge fan of universes with much content (Tolkien universe, Warhammer 40k, ...). I will create as much content as possible (backgroundstory for each race available,...).
The story will be dynamic and with huge effects. For exapmle everyone starts as human and depending on his behavior and choices he will convert to another race (do not worry this fits to the content).
For now we focus on making a alpha, after that beta, then publish whole game and then we will have time to think about keeping the players
One thing we agreed on is listening to the players what content shall be created. So if anyone has suggestions pls let us know.
One of the games which I was really impressed with (in terms of rich content) was this little gem called King of Dragons Pass. It was a boardgame style RPG, but with very intricate stories and "creation myths"... if you spent the hours required to read them, you'd have a better understanding of what worked culturally and socially in the game (it didn't practise what we'd consider as norms in our society). The style was wonderfully maintained throughout the game. The music worked. Even the 2d hand-drawn art was extremely complementary.
I played the PC version when it came out in the late 90s/early 2000s. It was considered a flop at the time, couldn't compete with the age of FPS and action-oriented RPG. But a few years back, they re-released the version for iOS and it was a huge hit. Updated only a few stories, but ported the entire game over and charged I think $5 for the game? Made them a lot of money... not bad for a game over 10 years old!
My point is... there's an entire generation of people who love a good story, now getting on with age. You might find them a huge part of your game if you build good content. And more importantly, that content has to be synonymous with your brand. It has to be consistent. Can't be sci-fi one time and suddenly horror fantasy, and then medieval when the writers change.
Sorry for being long-winded!