Does the Pope eat fish on Friday?
I guess what I'm about to say makes me the bastard of Charles Murray and Alan Bloom, much to my dismay. 'Fun' as a metric of success is about as useful as saying your lunch was 'successful' because you had 'fun' eating dessert. I have fun watching Nate Diaz videos on Youtube, but nobody really cares about my personal fun watching Youtube, and nobody should. A game is successful when it meets objective critera of success, like size, popularity, breaking new ground in the genre, and high technical and creative standards. If you are having fun on a game, that game is not necessarily successful. It's just... 'fun'. /rant