Is there anything that makes Christianity a more valid belief than a religion I make up right now on the spot?

Before the crucifixion
(or the destruction of the second temple, depending on your view)
Satan was the lawful ruler of planet Earth, and external magic worked
After the crucifixion Satan was defeated and Lord Jesus became the ruler
External magic no longer worked, but every ‘man’ became ‘his’ own magician
Humans have hardly scratched the surface of what each is now capable of

This has the effect that every person has the capacity to be their own religion
You are the god of your own universe
If you developed your will-power you could go into yourself and effect amazing changes

The main function and benefit of communal religion is communal worship of God
If any scientist would like to check, they will find that worship of God has beneficial physical, emotional and spiritual effects, and group worship increases those effects.

The larger established religions have the additional advantage of being directly connected to a Patron Planet in the Worship Worlds, which form the Lower Heaven.
This connection acts as a ‘fast track’ into Heaven, with lower barriers to selection.