[jbssm]

TL;DR: It's a logic truth, if you accept the Big Bang theory, then God couldn't exist before the beginning of the universe.

I think you didn't understand the premise here.

The premise is: "The Universe started in the Big Bang.", now, following from that premise it's impossible to have a God before the Big Bang.

You can contest the Big Bang theory and with it find a loophole for the existence of God, but the OP was finding it "amusing" and nonsensical what actually follows directly from accepting the Big Bang theory: God couldn't exist before the beginning of the Universe.

[livingparadox]

This assumes that the Universe contains God. Most understandings of a divine creator place him outside the bounds of the physical universe, and therefore immune to your argument. Unless you're referring to a specific idea of "God" that does include him/her/it as a part of the universe.

[jbssm]

If the God is outside the physical bounds of the Universe then he cannot interact with the Universe. From the moment the God can exert some change or even just observe parts of the universe then he must be within the physical bounds of the Universe.

Again, the issue here lies in your understanding of the Big Bang theory.

[livingparadox]

Let me present an alternative scenario, if a video game developer creates a virtual world, is he required to exist within the virtual world to exert any change or "even just observe parts" of the virtual world?

[micwawa]

Ok, but this is just playing with the word "before".