I think that the good life can be discovered objectively but in general terms, and I think that the good life is the life of maximal pleasure (in whatever term you want to call that, I first proposed satisfaction, then James proposed joy, and I think other terms could be proposed but at the bottom of it there is the feeling of maximal pleasure). What constitutes maximal pleasure for different individuals I think is subjective and changes.
You gave a few instances of what might be perceived as the good life, “being there” and “well-being” for example. I might hazard that when someone feels immersed in the experience of life in such a way as to call it the good life it is because it is something pleasurable, if the experience were unpleasurable it wouldn’t merit the name, and the same would go for what gives us well-being-
You also gave the instances of stoicism and epicureanism. As far as I know, Epicurus was a hedonist, he just felt that the highest form of pleasure was that which one felt from intellectual pursuits. And stoicism does often shun desires, but only because they feel that they are the cause of anguish, and so displeasure. I think even at the bottom of it when Socrates advocates moderation, it is because our drives for desire need to be moderated for a variety of reasons to experience maximum pleasure. If we follow our desires blindly we might not act prudently, and so fail in their acheivement… also if we glutton ourselves beyond measure we will become sick and not experience the pleasure from eating.
I also think that a lot of what we call civilized life are sublimations of deeper animal drives and desires to more socially safe practices, or else are processes which mediate our obtainment of them. I think the same goes for spirituality, either it is a similar position to the stoic one, or else it is the expression of sublimated desires and drives (sublimated being transformed, but the connection is still present in the pleasure it brings, which includes the belief that one has reached a higher state of being — like the belief in superiority, or else purpose).
Whether I am right or wrong in this, I think understanding what constitutes the good life is of utmost importance to philosophy because it underlies the way we interpret the world as well as the practical implications of our contemplation.