Addiction is fascinating because the distribution of outcomes is so broad across users. Damn near anything can be life-debilitatingly addictive to some segment of people while others can consume it with absolutely no problems.
Psychology obviously can't always be simplified, but I think a key component underlying when consumption goes in a bad direction is why someone is using.
If you're playing videogames because your life is otherwise fine and you want to sprinkle some leisure on top, it's fine. Hell, you can play for hours a day and it's not really a problem if you're content with the time spent.
But if you're playing videogames as an avoidance strategy for underlying psychological problems, then you're setting yourself up for addiction. Because avoidance tends to cause those problems to grow. You aren't working on them, and seeing yourself avoid them subconsciously sends a signal that the problem is too big for you to handle. So the whole time you're avoiding, you're building it up bigger and bigger.