Everything. The casual gamer puts family and friends first, video games being one way among others to get people together. The core gamer keeps his social life to a minimum so as to play more games, which is his most important activity. And when he does meet friends, it's only to play or discuss video games. He doesn't have a girlfriend because no real girl could possibly rival female game characters. Plus, with Project Diva f AR reality, he can insert cute girls in his daily life.
They also differ on how they manage their money. A Casual gamer buy mundane things such as clothes, food or insurance and then games with the remaining budget. The core gamer puts all his resources in gaming and doesn't know the correct price of products other than video games. He doesn't eat anything except Calorie Mate because Snake does in Metal Gear Solid 3.
The core gamer may know Japanese, strange gaming vocabulary, complicated strategies and all kinds of button inputs, but he doesn't know how to use an iron, a washing-machine, an oven or a social insurance program and has to rely on casual gamers to teach him about those.
Notice : everything I've just said is ludicrous and only applies to me.
