Your question comes from many Christians wanting to believe only part of the scriptures but not ALL of the scriptures. Not everyone is going to Heaven... that is the calling of a select few 144,000 (12,000 from each of the 12 Tribes of Israel)... But just today there are more than that number of Christians worldwide.
But it is written that the Earth was made to be inhabited. It was also written the meek shall inherit the Earth. The word meek originally meant teachable.
After Armageddon and the Judgement passed upon Satan, and his unrighteousness, and his System of Things, Sin will not be inherent to men any longer, but then it will come down to a decision are people willing to serve God as "He" spells it out, or "do their own thing." Those that serve willingly will prosper, and live, those who choose their "own path" will be looking to disconnect from God, and in essence disconnect themselves from the source of life... So they are choosing to die. Eventually at least. Freedom of Choice will always allow a man to choose to walk way from the living God,but that in no means requires that God "reward his unfaithfulness." But since there is no Hell the only thing that will occur to them is they will die, and be conscious of nothing.
The Righteous, and the Unrighteous are garunteed the same thing an eternity without pain and suffering, the faithful (righteous) have only one added benefit... Life.
The Sin Adam committed was based in the fact that he did not correct Eve. Eve was decieved by an Angel who later was known by the title Satan the Devil. We were not designed to resist Angels, since when everything went according to plan Angels were messengers of God.
The difference from this world where Sin is born in every man. In Paradise each man's sin will be their own, not an entire race doomed to a particular fate (ie:death), but each will be responsible for their OWN choices.
If you really want to know what the Bible Really Teaches, go to www.watchtower.org and ask for the free book "What Does the Bible Really Teach?"