It's no different to playing 5 different games in smaller times of frame equally over a week as you would 1 game.
In some instances people confuse this with addiction, because they only see one game.
Personally, I went back to WoW with two real life friends a week ago and started from scratch, it's fun to play with them, we do play abnormal hours, but I go to college so I have to be tight with money, so staying in playing 1 game appeals to me.
It's not like I would be going out anyway, going off topic here though.
But taking time off work deliberatly to play more are tell tale signs of the start of one, or they simply like it. Usually addictions have major health problems but as long as that person maintains a decent level of health, hygiene, eats and can even work I would call it a hobbie. Gaming, love it.
Throwing the word addiction around for gaming is different, it's not like drugs or alcohol.