What is the most popular theory to how the world began?

Answer 1

Since the question is in the religion and spirituality category...

The three Abrahamic religions (Judaism, Christianity, Islam) are in substantial agreement that the world was created by the Creator (JHVH, God, Allah respectively). Collectively these three religions account for the majority of people in the world.

If the question had been in a science category, the Big Bang theory is very nearly universally accepted; there is substantial physical evidence for it, and while there are a few open questions (what's up with the inflationary period; is there really a cosmological constant;string theory/M-theory/something else), there aren't that many cosmologists who disagree with the whole thing.