There is this boy that has liked me for over a year, and finally I like him back now too. He is very kind and considerate towards me and I have strong feelings for him. We have been best friends for a while now. He recently asked to start a relationship but I declined, telling him that although I do like him, there are personal barriers that I have to overcome first.
However, I just recently learned that the only activities he really does are going on the computer and watching TV. He plays WoW for hours after school and spends most of his weekend doing so too.
I don't mind if people spend a couple weeks playing games, it's just a hobby and such. But to the point that it's so obsessive, I can't tolerate it. I wouldn't want me partner to be this lazy, and frankly, rather boring.
Other people are free to spend their time as they like but this is a major turnoff for me regarding a romantic partner.
Should I mention this reason? I feel like I would be asking him to change and I feel guilty about that, but I know that I would never date someone who is addicted to the internet and TV, so there isn't any hope for a relationship and I would just be leading him on. . . what should I do?

If I was you I would be honest and tell him the truth. I was soooo the same way when I was in my dating stage. I met my child's father, I didn't no he was a gamer. I was upset in the begging about him playing the game all the time. I didn't no what to do or what to say. Then enough was enough and I set him down and told him how I FELT then afterwords he cut back on his game time. I have no problem with him playing the game. When he plays the game now I use the time as me time and I relax and or do my own thing. I enjoy it because I am not the type who want a lot of attention so I enjoy my free time.