Mark 1:14-15 (New International Version)
14 After John was put in prison, Jesus went into Galilee, proclaiming the good news of God. 15 “The time has come,” he said. “The kingdom of God has come near. Repent and believe the good news!”
Matthew 4:17 (Young's Literal Translation)
17From that time began Jesus to proclaim and to say, `Reform ye, for come nigh hath the reign of the heavens.'
What people do to have heaven on earth? What amount of money would they pay? What length would they go to have a taste of heaven? Mankind has tried for ages to have utopia in this world, an ideal community or society possessing a perfect socio-politico-legal system, an attempt to create an ideal society where everyone lives in harmony.
The Jews of Jesus time felt that if the Messiah came and conquered all of their oppressors, they would have their utopian Kingdom of God. The Romans of the day felt that as long as they subjugated all of the inhabitants of the known world and created the perfect Republic, wherein the "beauties of society" reigned as Plato had written about, they would have the perfect world.
If you look at different translations, you will notice that the Kingdom of Heaven, or the Kingdom of God, can be translated as the "reign of the heavens" or "kingdom of the skies". Jesus entered the world in human form to tell the inhabitants that they could live under the authority, grace and mercy of God. He was there to point them back to God and His divine love.
He was there to show them how to be reconciled to God and to proclaim God's kingdom here on earth as well as eternally in heaven. He was there to truly establish the perfected kingdom and restore God's perfect creation.