> what if it were primarily defined by altruism?

It's a fun question, but I think the answer is less entertaining: we would all be less happy. The fact is that most people are better at guessing what they themselves really want than other people are. It's a question of information. I know more about my desires than my friends do, for the most part.

Altruism is nice, but inefficient.

Spending quality time with friends & family, on the other hand, truly is priceless. I don't want them to be nice to me - I just want to be with them. So finding an economic (and cultural) system - be it a few tweaks on the current one or a radical rethink - that gives me more opportunities for a healthy social/family life ought to be the goal, in my opinion.