B/X Known World
If you haven’t read the MDA article that poster linked you should take the time. It’s a breakdown of several types of fun in video games, an analysis of what desires those types of fun serve, and how to serve them in game design. It’s a short article but it is rather good. It speaks direct to the topic.Again, as I just articulated ... if someone is telling you that the reason that they play a game is because the game is fun, then if your interest is in finding out why the game is fun, you should ask them what they enjoy about it. They may or may not be able to articulate it, but they aren't lying to you about their enjoyment.
If, on the other hand, when someone tells you that they find something fun, and you feel the need to "pushback," then you are likely not paying attention to what I just spent time writing.