God created us to spend eternity with Him in heaven, but through our sin--by our most grievous fault, the gates of heaven were shut to us. This was not done maliciously by God--He didn't exclude us rather, by our choosing to sin, we excluded ourselves from eternal joy.
God desires to have each one of us in heaven with Him, sharing in His perfect happiness. His desire for us is as infinite as His love, His desire isn't a minor one, like "Yeah, you guys can crash on my couch in heaven for a while, here's a blanket." He is infinite, and so His desire for us is stronger than any we can possibly imagine. He gave His only Son for us, through Christ, God threw open the gates of heaven in order to bring us to Him. He didn't just open the gates though, He isn't just packing us all into some sort of eternal subway station, He has prepared places of honor for us at His table and has set a great feast for us, and like the father in the parable of the prodigal son, He rejoices whenever one of us sinners returns to Him, and all of the saints and angels in heaven rejoice with Him. So great is His love for us.