We are all individuals. We should live naturally.
Don't live for some duty, for some God. Live for yourself. Live for the individual.
Sadly, it appears that this message of Terranigma is commonly misunderstood, and people believe the game promotes self-sacrifice and bowing down to nature, when it's in fact about the beauty of humanity that allows us to conceptualize reality on a grand scale and create.

The gardener caring for his pretty pumpkins is happy and prideful because of his own accomplishments, because he lives for himself.
The butcher is happy because he can create a new meal.
The inventor is happy because he himself invented airplanes that will allow all of humanity, including himself, to improve.

And finally, Ark, the protagonist, is happy and filled with pride, because he helped the world grow. He learned, he improved, which is the greatest joy there is.
In the end, he's not rewarded with death. The game does NOT contradict its own message by hypocritically having the protagonist die for his duty, for a God, for someone other than himself. Rather, he is gifted with a dream, flying through the world in pride, knowing he was what led to this beautiful earth. And afterwards, although his journey as a hero is over, he will continue to live on. For himself. In happiness, together with his beloved.