The Moon is very large compared to the Earth - I have seen the Earth/Moon described as a double planet. How it formed (most likely a collision) is very, very unlikely.
All the other moons in the solar system are nowhere near large enough to stabilise the planet's axis of rotation.
The Moon also has the same rotation and revolution time, so that it always shows the same face to us. I've always wondered if having different rotation and revolution times could have helped humankind to consider the existence of spherical planets a lot before, hence helping progress.
All the other moons in the solar system are nowhere near large enough to stabilise the planet's axis of rotation.