It's interesting how many people bring that up to me when talking about religion. My best friend is Muslim, and she often says that if Islam is not the true religion, then there wouldn't be so many converts. She also says that Islam is the true religion because her Muslim friends follow their religion piously, while most of her Christian friends, except for some notable exceptions, don't even follow what they teach. Regretably, it is true that countless Christians have lost sight of the Christ, whom they profess to follow. It is also true, however, that there are good and bad in all religions. Even many atheists are good people. To bring up numbers, therefore, is not so important, since numbers go both ways.
The main thing to remember is that the issue of numbers has nothing to add to the validity of truth. In fact, if I ever looked at numbers, I would feel discouraged since I am from one of the minor Christian denominations, whose teachings often differ from mainstream Christianity. I still believe, for example, on the Biblical Sabbath. If I looked at numbers, I also would be a Christian by name only, and not by deeds, since I see so many Christians doing the same. Therefore, I do not look at numbers, and instead look on whether or not I am founded on the truth of the Word of God. That is the bottom line.
Irrevocably, the truth remains truth, whether or not I chose to believe and follow it. Most of the world is lost in sin; some claiming some kind of religion, but never really following it; others believing in no God at all. All this is of no consequence. The truth does not depend on how many people follow it.
In fact, the Bible teaches that many will not chose the way of life; that regretably, the majority will be lost. Jesus, himself, taught this:
Matthew 7:13, 14 -- Enter by the narrow gate; for wide is the gate and broad is the way that leads to destruction, and there are many who go in by it. Because narrow is the gate and difficult is the way which leads to life, and there are a few who find it.
Luke 13:23, 24 -- Then one said to Him, "Lord, are there few who are saved?" And He said to them, "Strive to enter through the narrow gate, for many, I say to you, will seek to enter and will not be able."
I pray that God will bless all of us, and open our hearts to the working power of the Holy Spirit, as we wholeheartedly seek to know him and his eternal truth.
And you will know that truth and the truth will set you free. (John 8:32)