A myth, @bookish1? If you were all alone, and no one would look at you or talk to you or deal with you in any way, how do you think you would do? Could you even survive? For how long?
Humans are tribal creatures. We survive because we cooperate. It is very difficult for a human to survive alone, and the genes of a human who is alone all their life will certainly not be passed along. They will be an evolutionary dead end. Without relationships, we make no measurable impact on this planet. A year after your death, it is highly unlikely that anyone or anything could find evidence that you had ever existed.
It is only in relationship that our lives can have any meaning outside of the meaning we give it on our own. We can only survive past death because of relationships. We only survive in memory of others.
Now you talk about happiness, which is a nebulous concept. But most things that give people happiness: food, shelter, companionship, meaning, etc are created more easily and effectively in relationship with others. If relationships are not the most important thing, it seems like you would have a rather impoverished life, both in material ways and in psychological and spiritual ways. Even a relationship with God is a relationship with a person-like entity.
I would argue that relationships are the most important thing, and even more so if you don’t have any. But of course, you do have plenty, even if the only ones you have are on fluther. I know that isn’t the case.