While it is obvious that YOU are referring to Christianity, and trying desperately (again... sigh) to disrespect it, if you are referring to ALL religions that believe in god, God, or gods, then you are talking about fully 90% of the world's population that have some faith in some form of religion and supreme being(s).
But since you are "aiming" at Christianity, you are under the misconception that Christians convert people. Christians do NOT convert people. The Holy Spirit and the individual are the ones who convert. Christians are merely the "Gospel-givers." Jesus said to His disciples (Matthew 28:19-20), "Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. Amen." The term used is TEACH, not CONVERT.
The Scriptures also tell us that "Many are called but few are chosen." In other words, sad though it may be, that most people will reject Christ, so it shouldn't come as any shock that "the majority of the world does not believe." It is a Christian's firm desire that ALL should come to faith in Christ, but we know, as Christ did, that this will simply not be the case.
Besides, God does not measure success by mere numbers.
MARANATHA! Come, Lord Jesus, COME!