Yes, the weight of evidence (rimshot!) is certainly on the side of genetics, which is not to say that someone likely to gain weight cannot be at a healthy weight either. I think we all get the notion that genetics set the stage, but they don't close the curtain. Many Native Americans (of Northern descent) have genetics which make them prone to alcoholism, but by no means does that doom that person to being an alcoholic. (reference: http://www.guilford.edu/original/Academic/chemistry/current_courses/chem110/ringwalt.html [Broken] )
If, as Proton Soup has said regarding an abundance of rich foods, they had no access to alcohol in the necessary quantities, it would be a moot point. Likewise, different metabolism doesn't makes it harder to stay off the sauce once introduced, but it is still not a forgone conclusion.
As with food, to say that this is a purely social/environmental problem is misleading, and to say it is purely genetic is misleading. HOWEVER, take away one of those factors, modify the genetics for lipid storage or alcohol metabolism, and you are a long way to fixing the problem. As food and booze are unlikely to vanish anytime soon, in practical terms this has become a genetic issue, and one of how the individual is nurtured.