Why isn't it enough just to be a good person?

Christianity is not first and foremost about morality; it is about relationship. God is a person, not a thing, and desires that we relate to Him as a person. If He is the creator, the One in whom all things begin and in whom all things find their completion, then it is with Him that fullness of life is found.

The same is true about our future. Scripture describes heaven as the place where God is. It isn't some perfect amusement park that we somehow squeak into by the skin of our teeth. If we embrace Jesus now, then heaven is the place where that relationship continues without our current hindrances and ignorance. Hell is described as relational separation from God. It is the option for those who would not enjoy God's presence. Hell is a dead end, since further growth springs from intimacy God.