Yes, it's possible to become addicted to just about anything -- not just alcohol or drugs (although those can be devastating), but also things like food or gambling, shopping, or exercise. When we become addicted to something, we become so absorbed that it begins to control our lives, and we often can't break away on our own.
As I read your letter, I couldn't help but wonder if your husband has ever asked himself why he's become so absorbed with playing games on his computer. I'm not a psychologist, of course, and I don't know how your husband would answer -- but from what you say, I can't help but feel that he's doing this to escape from the harsh reality of being unemployed. This is often the case with addictions.
What can you do? First, assure him of your love, and that you don't look down on him because he lost his job. We live in difficult economic times, and we need to pray for our leaders as they seek answers to these problems. Then encourage your husband not to give up, but to keep looking for a job -- and even consider some type of retraining.
Most of all, commit your lives and your future to Christ. God knows what you are facing -- and He knows your future. The Bible says, "If any of you lacks wisdom, he should ask God, who gives generously to all without finding fault, and it will be given to him" (James 1:5).