Debating about addiction is complicated because everyone thinks they know about it, but very few know the scientific literature and the debates about it. Take this article (written by a neuroscientist) about "internet addiction":

http://www.mindhacks.com/blog/2007/08/why_there_is_no_such.html

As mentioned in this same article, whether gaming is indeed considered (scientifically) as addictive is still up for debate. Also of note are the differences between "compulsion" and "addiction", and just because someone does something "too much" it doesn't characterize an addiction.