I've had this discussion with a few people: and afaict for some folks it's not actually an addiction, but a passion. I think the difference lies in whether you ever have the thought: "I wish I was doing something else right now", and then continued doing what you were doing. It comes down to whether you're in control of your own motivation and time.

Hobbies are great, and video games are a perfectly legitimate hobby, for some. Just like some people can casually do cocaine and not think about it the next day. For others, it's a different story.