Something becomes an addiction when it is unreasonably difficult to stop doing it in order to address something you would consciously rate as more important. That could mean biological needs like food or sleep, social needs like work or seeing friends and family, or self-improvement like exercise or pursuing hobbies other than video games. It is not determined primarily by hours spent.

Of course if you have no other hobbies, never exercise, don't have friends, and actively minimize other time commitments to maximize the time you can spend gaming, most people would consider your lifestyle imbalanced. That doesn't make it an addiction though, and if you're an adult, what kind of lifestyle you want is ultimately up to you.