I’d everyone else died of old age and you are the last, would you still want to leave the earth better than you found it?

Yes. Humans are not the only thing existing on this planet, and I find it rather arrogant to treat it this way. If I’m alone staring down the heat death of our universe? Well it doesn’t quite matter anymore.

Would you take comfort in or be indifferent to the happiness you brought

Absolutely. This is probably more nurture vs nature though. I’m very much an atheist but was raised in a strong Christian household. I’ve shunned the religious aspect, but “Love your neighbor as yourself” is pretty much ingrained in my DNA at this point. I find happiness in bringing it to others.

As for ideas of good and better, of course they are my own opinions and based on experiences of others. There is no objective “good” and “better”, because there is no objectively true meaning to life. For me personally, doing what makes me happy would include eating good food, drinking good whiskey and listening to punk rock. Those are not objectively good, but they are good to me. I will share them with likeminded people, and I will find other ways to better my neighbors’ lives.