What do you think of a 26 year old who still lives at home and plays World of Warcraft?

Is it you? No, I don't think he's a loser. If he has no desire to get married and start a family, it would be a big mistake to do that. If he is happy with his life that's all that matters, but if he wants to have more friends and possibly a girlfriend then he should find someone who accepts him for who he is.