Yes, there is a God, but of course simply saying that God exists does not mean there is one. The existence of God has been debated for centuries. Atheists deny him, or say they “lack belief in God.” We Christians, of course, not only believe in God but also claim to have a relationship with him through the person of Jesus Christ who has been revealed in the four Gospels of the New Testament. These four Gospels are historical documents that tell us who he was and what he did. They let us know that he claimed to be God in flesh. Consider Exodus 3:14 of the Old Testament when Moses asked God what his name was, God responded with, “I am that I am. Thus you shall say to the sons of Israel, I am has sent me to you.” In John 8:58 Jesus said, “...before Abraham was, I am.” Whatever you might think of Jesus, according to the Gospels he claimed to be God. So, if you believe Jesus, then God exists.
Proving that God exists is another matter. But, you see, proof is for mathematics and logic. How do you “prove” there is a Great Being outside of our universe? Do we look for footprints in a riverbed? Do we examine evidence under a microscope and say, "A ha! There's God!"? That would be the wrong approach. If God exists, he would be beyond our universe, non-material, and transcendent. So, we would have to look for evidence that is consistent with a non-material and transcendent being.
Whatever argument you might accept or deny, it seems that your presuppositions are what determine if you believe in God or not. Atheists, of course, presuppose that God does not exist - by faith. They can't "know" he doesn't exist, nor can they prove that in all the universe (or outside of it) there is no God. But, their atheism means they will deny any evidences or explanations used to affirm his existence. On the other hand, Christians who claim to have an encounter with God rely on the revelation of Scripture to tell them who Christ is and who God is.
I have to ask, how could there not be a God? Look around you. The heavens declare the glory of God (Psalm 19:1). Consider the vastness of the universe, the perfection of the balance of life, and the incredible complexity of the information structures in DNA. Are we to believe that the super-complex information structures in the DNA molecule are the result of chance? Is life an accident? What about beauty? Is it nothing more than a chemical reaction in the brain? What about morality? Are there any moral absolutes such as, “It is always wrong to torture a baby to death merely for one’s personal pleasure”? Or, is such a moral absolute nothing more than the result of chemical reactions in our brains? If so, how does one chemical reaction which leads to another chemical reaction produce moral absolutes or even logical absolutes? Is it easier to conclude that such truths are the result of chemical reactions and brain wiring, or that they are authored by God? Is morality merely the situational-based whims of people’s preferences? Is the beauty of a sunset and the wonder of a new born baby's precious life a byproduct of the survival of the fittest?