Well, I think the more disastrous one here is addiction. If someone is greedy, it only means he wants more, but if he doesn't have the means to get it, he will forget it, but in addiction, there is nothing you can do about it, because addiction goes straight to stay in your blood and becomes your behavior. Once you are addicted to something, whether it's good or bad, you will always want to be doing that particular thing ,and you will find it difficult to stop, and then it turns to be your behavior. Imagine someone having a gambling behavior, that means he cannot survive without it, so even if addiction and greed work hand in hand, I still prefer greed to addiction.
You hit the nail by the head because there is no basis for comparing greed and gambling addiction. Greed is just a one part of gambling addiction, the most significant one. I think greed is like the driving force for gambling addiction because if you remove great from a gambler, the zeal to persist in gambling after a loss will not be there. Although, some gambling addicts just derive joy gambling even though they are not winning, it has become a sort of hobby, something without which they feel incomplete. At this point, it begins to appear like it has no business with greed but on a broader note, it does have everything to do with greed.