Similarly to Phil and La, I’d say I’ve been obsessive about a game here and there. Certainly to the point of all my free time being spent on the game. I think that’s where the line is though, even spending all your free time on something can be ok, it’s when yoy deliberately start making time by skipping school, work etc.
Though I also find with any hobby of mine, if I’m absorbed in it too much I find myself through burning out or boredom wanting to do my other hobbies more until it breaks the obsession.