Is God a Honda or Volkswagen?
My friend just bought his wife a car as a present. He gave her a Honda.
Now let's say we have to guess what's her car. Is it a Volkswagen? Toyota? Ford? Porsche? Audi? Mazda? Hyundai?
Here's the thing. If it's left up to us to guess, we have 100s of options. It could be any type of car. Your guess is literally just as good as mine. Who's to say my guess should be privileged over yours?
But if our friend reveals that it's a Honda, then we don't need to guess. And we can't say "But how do you know it's not a Toyota or Volkswagen?" Because, simply, he is the one who sent the car as a present, and he has revealed to us what it is. It's not a game of guess.
It's the same with God. If it was a game of guess - God could be any type of God or gods. And who's to say that my guess is any better than yours?
But God has sent us his Son Jesus, and revealed that we know God by knowing Jesus.
But why is it Jesus and not some other God or gods? Because, simply, God is the one who sent Jesus and has revealed to us who he is. It's not a game of guess.