Yes, perhaps some are faking their commitment to Christ; even one of Jesus' closest disciples (Judas) turned out to be a fake. He was only following Jesus because of what he selfishly thought he could gain from it, not because he really believed.
But does that mean no one has ever believed in Jesus and had their life turned around? No, certainly not. God delights in taking even the most rebellious person and changing them through the power of Christ. As the Bible says, the Gospel is "the power of God for the salvation of everyone who believes" (Romans 1:16).
In fact, the same day I received your letter I also received a report about an evangelist I have never met who is making a deep impact on many lives. His background? He was a prisoner, but one day he met Jesus Christ and his life was dramatically changed. He is a living example of the Bible's promise: "Therefore, if anyone is in Christ, he is a new creation; the old has gone, the new has come!" (2 Corinthians 5:17).
And this is God's promise to you. Why serve the devil any longer? Why allow him to continue to deceive you? Your life can be different if you only open your heart and life to Christ. Make your commitment to Him today.