Here is probably what you may call a 'reformed addict' writing.
Won't bore you with my case that's somehow different from inside from your friend's one, just jump to my conclusions.
People starts playing games because they're fun.
But they keeps playing for other reasons.
I belive in the end they think their life sucks.
(they don't realize that, so don't tell them, they won't understand).
And they don't care a fuck if people in the world dies, are hungry, have terminal-diseases, and so on. In the end it's simple:
comparing your options with the options of people around you, if yours are worst, you have to choices:
1) make your options better
2) choose something easier than life
This reminds a bit the 'Trainspotting' slogan, trust me, it's even about addiction, but this isn't started from that.
Obviously the second choice is easier.
As a huge-ego-self-considering-smart guy, i enjoied that MMO so much because the rules ( and sometimes, why not, break them ) were relly simple. They have to be, since if they won't people won't play and software houses won't earn. So if rules are simple, it's easy to make plans, it's easy do act smarter than the others and self-realize yourself winning something ( being the best pvp player or the king of the richest town or whatever ).
Actually while you play you don't think it's easy. You think it's easy for you, since if it would be easy for everyone, others won't be loosers. This is why you keep playing.
Because it's easier, and sometimes it even makes you feel more realized than how would you will in real life. That's sad.
This was my way out:
On one side, i was still making this reasoning while playing, so i shame myself in front of others and used to play during night, still going class in the day, even with bad results, still going out with friends, even if i was hurry inside to go back home, and so on.
On the other side i was luck. I used to play in an unofficial server and i ruled it. Being at the top makes you get that it's just a matter of time before someone will reach you, and the only way you have to be still at the top is going faster and never stop. But it's a challenge with the developers of the game, and they can't really provide ways to going on playing, still having fun without changing somehow the rules.
When lots of rules changes, you finally got that your 'second-life' is in the hands of some programmers somewhere in korea.
That's exactly the time i stopped finding playing a fun. ( it wasn't from long time before but does it makes difference if you don't get it ? )
The way out from MMO is, in the end, both simple but hard : you have to reason with the player, to make him get that life is a better challenge to take.
Try getting him into some experiences, outside trips, travels, parties, why not? girls or whatever he/she likes.
People are all different, if you konw him find things in RL he most likes, and reminds him they're still there and they will be there after his server will be destroyed by a fool with a sledgehammer.
Regards