You're probably thinking of these words in the Gospel of John: "No one has ever seen God, but God the One and Only, who is at the Father's side, has made him known" (John 1:18). (The title "God the One and Only" refers to Jesus Christ.)
No, these words don't mean that no one ever went to heaven before Jesus Christ came into the world to save us. They simply mean that no living person has ever ascended into heaven and seen God, and then come back to earth to reveal God to us. Some (like Moses when he received the Ten Commandments) were given glimpses of God's glory -- but they didn't ascend into heaven until their deaths.
But don't overlook the central point: One person has come down from heaven to reveal God to us -- and that is Jesus Christ. Do you want to know what God is like? Look at Jesus Christ, for He was God in human form. The Bible says, "In Christ all the fullness of the Deity lives in bodily form" (Colossians 2:9).
What do we learn about God when we look at Jesus? First, we learn of God's love for us -- a love so great that He was willing to leave heaven's glory and die for our salvation. We learn too that God wants us to spend eternity with Him -- and this becomes a reality as we give our lives to Christ and trust Him as our Savior and Lord.
Because of Christ we have hope -- hope for God's help with our daily struggles, and hope for life with Him in heaven forever. Give yourself to Christ today.