That is a ridiculous question and one that has no answer. We can ask, What is the oldest religion? Or Which religion is the most relevant to today's world? Or Which religion is the most widespread throughout the world? Ow Which religion is the fastest growing? But which is best? is like asking which is the best grade in school, first, fifth or tenth? Each has its place, each provides what is needed for the time, each is part of an ongoing process. And most important, each is from God and is a part of His plan for mankind.
So you decide. Be fair and open minded. You, and only you, can answer this question.