I think there is no single answer to that question. But your observation is right : if you provide something that players are familiar with and then you add a twist to it, the game becomes suddenly appealing.

Take PREY for example: a mediocre shooter, but with portals and walkways where you shoot enemies upside down! - WHOAW!

I, for example, hate classic shooters. They are dumb as f***and I f****** hate those f****** skilled pro-players which don't let me play for just one second after I spawned - I don't get the fun in that.

However, that twist in PREY or the horror story in FEAR made me play the games (and the stencil shadows, they were gorgeous!). Or the Suffering or Max Payne: great story, f****** terrifying monsters and über-cool moves while pulling the trigger.. that was fun!

So in the end the customer picks what seems to be fun.