You're right; polls today certainly indicate that most people still believe in God. And yet you're also right when you say that God doesn't seem to make much of a difference in the way they live (at least for many of them). Why is this?
Let me answer by asking another question: Whose fault is this? Is it God's fault, or is it ours? I think you know the answer. You see, it's entirely possible to believe in God, and yet not take Him seriously. It's somewhat like being sick, and having the doctor prescribe something that will cure our illness. We can get the prescription filled... we can believe it will cure us... but if we put it in the medicine cabinet and never take it, it won't do us any good.
The same is true with God. We may believe in Him... we may even believe He can help us, but if we ignore Him and leave Him out of our lives, nothing will change. Instead of following Him, we'll act almost as if He didn't exist. The Bible says, "You believe that there is one God. Good! Even the demons believe that" (James 2:19).
Don't let this be true of you. Don't just believe in God, but put your belief into action, by committing your life to Jesus Christ. Then make it your goal to live for Him every day. As the Bible says, "Do not merely listen to the word, and so deceive yourselves. Do what it says" (James 1:22).