There is very scant data for me to analyze, when it comes to learning what sells. the Mneme world generator I know sells as it hits silver this year. As for what will drive more people to adopt it, i can only guess accessibility.
So I have high praises for Seth Skorkowsky as when ever he reviews an adventure, he polishes it so much that I feel tempted to buy it immediately and run it. He cleans the maps, identifies plot problems (inconsistencies that will stall the game), and various other insights - I'm sure its not just him but his players pointing out errors in the writing.
What Seth does is make the game more accessibile. I think thats what it all culminates as there is less and less reason why I or anyone should not just buy the product. I want to do what he does - and the really nice way he corrects it without turning people off the adventure.
Well I want to do that to Cepheus Engine - coming from GURPS and having people have a hard time getting into GURPS - Cepheus engine fixes that by being more accessible. Not only are you able to make an adventure in Cepheus Engine - but you can publish that adventure. If your players really like it to the point that they leave reviews - then you have a great source of validation.
So what can I do to make Cepheus Engine more accessible -
- well provide Creative Commons Art and Ships
- tools to speed up character creation, ship creation, world creation
- tools to create scenarios someone who wants to improvise and challenge themselves (using RNGs).
- accessible sample settings - not just any other setting but the open source setting which complements the tools and rules.
Of course why didnt it work with Mneme Space Combat? I think its because space combat is not often done. I've read no complaints about space combat rules of any other CE system - and no one is perfect. I have to guess, specifically conscious of my pain points when I run a CE game.