Anything to the point of over excessive could be considered addiction. Look at the South Korean man who died of cardiac arrest in an internet cafe after a 3-day gaming binge. I think if you're unable to function, or your gaming lifestyle gets in the way of everything else in your life, then yeah, its an addiction. If you lose your job, your marriage falls apart, and you isolate yourself from loved ones, then you need to seek professional help. When gaming comes first before all else, it is addiction.
Now, if you're like me, and like the better part of the gaming community, I feel its a great hobby. Gaming is a way for me to wind down after a long day of work, and it allows me to get away from the stress of the world. I can turn on the A/C, some music, and play as a hero for awhile, or play some hockey with my son. You just have to break away and enjoy life here and there.