I have delt with people that had addictions and all I can say is if you express yourself to him the only good that comes out of it is that it may give him a little extra insentive to quit. It could be the thing that gets him ready to quit. Unfortunatly however much you try to will him to quit it won't be enough. I'm not saying that you should give up on him, never give up, but realize that this is something you can't control.
As an example, my father smoking:
I remember how when I was about 6 years old we had a smoking awarness class in school. They showed what healthy lungs looked like and what a smokers lungs looked like. It was really scary, especially at that age, because all I heard is "Your father is going to die!". So over the next couple weeks I had drawn several pictures of my fathers lungs being shrivled and unhealthy, or of him being dead, ect. He eventually saw those pictures and it was one of the only times I saw him cry. I can imagine the motivation that gave him but I can also imagine the extra guilt he must have felt when he failed. He told me later in life that each time he tried to quit it was for everyone other than himself. He tried quitting for my sister, my mom, for me and none of those ever worked. When he was finally able to quit it was because he was ready to quit for himself.
I'm sure he has had many nights wishing he wasn't always drinking. I'm sure he has some deep fellings of guilt about it. All I can say is to let him know how you feel, be there for him, and especially if he tries and fails be there for him so that he knows while he might have failed at trying to quit drinking he hasn't failed/lost you.
Goodluck.