I don't agree that this is a sign of Depression or that you are in anyway to blame for this problem! This is classical addiction, the same type that we treat alcoholics, shoplifters and druggies for. It is not going to yield to amateur attempts to change it.
I advise you to seek professional assistance. We often have to do an intervention for video games, just as we do for alcohol and drugs. Recovery is difficult, but it is possible. The first thing to go has to be the computer or, at least, the internet connection. I have even had to deal with cases where the internet was accessed via a dialup modem! Once the games are gone for good, healing can begin.
Don't think that you have to divorce the bum or toss him out on his ear! Most men come around in a short time, but most of them will go right back if given the chance!
I have found that therapy is an absolute necessity, but the traditional stuff is slow and painfully expensive. Look at http://www.emofree.com/
for some ideas about where to get help that won't break the bank.
I hope that you find help and that your guy can become the man and the father that he needs to be.