> Marketing.
again, no.
while i feel your pain and the cognotive dissonance associated with "it can't be that i don't make decent games! it has to be someone else's fault!" -- i have hard, objective data that disagrees with you.
i have assembled the funnel-and-churn data. i've put together the reports greenlighting games because the ltv has exceeded the cost of acquisition. i've used average instead of median so our whales inflated the reports. and after all of that, i've seen their 30-day retention numbers still stagnate.
i lived that for two years.
then, the retention bottom fell out. we burned through all of the naive and all that was left was a cadre of seasoned "me too" recognizing gamers.
https://www.google.com/finance?chdnp=1&chdd=1&chds=1&chdv=1&...
complain about clash of clans' business model all you want -- it's a quality game.
also please note, i'm not saying marketing isn't important, it's just not even close to "the most important" especially depending on the situation. if you have a giant budget with a ton of developers, it's pretty important. if you are a small shop where everyone has day jobs and you can endure slower, organic growth? it's not worth the money.