I gauge an alcoholic not by how much they drink, but rather how the drink affects their behavior, their relationships and their lives. If these things get all messed up and the person continues to drink anyway... then chances are they have a problem.
I did some pretty regular and heavy party drinking in my younger days, but outgrew it as I got older and matured. I never became an alcoholic. Some people do and some don't. Now, I hardly ever drink. I don't frown upon it... I'm just not interested.