In one sense, you are right; God made every one of us, and we owe our existence to Him and Him alone. The Bible says, "From one man (Adam) he made all the nations, that they should inhabit the whole earth... We are his offspring" (Acts 17:26,28).
But the Bible also tells us that something drastic has happened to the human race. Instead of being His children and able to call Him our Heavenly Father, our relationship with God has been broken. We're like a family that's been shattered by conflict and broken relationships, and we've even renounced our membership in that family, the family of God. The reason can be summed up in one little word: sin. The Bible says the human race has become "separated from the life of God... due to the hardening of their hearts" (Ephesians 4:18).
Our greatest need is to be reconciled to God and become members of His family. And the greatest news we will ever hear is that this is possible, because God has made it possible! God loves us, in spite of our sin and rebellion, and in His love He sent His Son, Jesus Christ, into the world to bring us back to Himself.
When we turn to Christ in repentance and faith, God forgives all our sins. But He does more than that: He makes us part of His family! We become His children! And someday we will go to be with Him forever in heaven. Why not become God's child today, by committing your life to Jesus?