My reply would be, "If God designed the world and life, then who designed God?"

If you can't create something out of nothing, then what did God create the universe out of? That means that God must have created the Universe out of pre-existent something. So, where did this pre-existent something come from if it couldn't have come out of nothing and God didn't create it?

I prefer the logic of the selfish gene

If you get a chance look up argument from ignorance. It's basically, i can't think of anything else... therefore it must be god/s, fairies, or the flying spaghetti monster.
None the less, there are some problems with the question. What makes you think it is created? What makes you think there is a who or what that did it? We could then go into where did that come from, but then they'll just use "special pleading (also check out if you get the chance)" and say that god/s always existed and don't have, need, or you wouldn't understand the explanation.
For fun though... and I implore you to broach this topic... "you can't create something from nothing."
What is nothing? It is nonsensical. Ask them do describe it. Ask if they have ever experienced nothing. Ask if they have a nothing to test to see if we can't get anything from it. Because if you describe nothing, in the philosophical sense of ex nilo, then you are talking about nothing as if it is something. You cannot describe non-existence, because it doesn't exist. I cannot even fathom what nothing is, because I've only lived in of universe of things like everyone else. Now if you could produce nothing and then somehow show that only nothing can come from it (which would be proving a negative which would take eternity, because we can't know if nothing can or can't create anything unless we have eternity to observe it) then you could say nothing comes from nothing..
I hope I didn't go to far off the rails here, but the concept of nothing is crazy. In the end, atheism has always been the same case since Socrates. That is..."I don't believe you, so prove it. Then I'll believe you."

This argument falls apart when it violates its own premise. Does god not have a creator?

Yes, nearly every time one visits my door… ‘Then how’d everything get here?’ We evolved from simpler forms of life … further back than most can comprehend. How old do you think the world is ..ask I

If we don’t believe in ‘a creator,’ why speculate? They’ve made that claim, it’s up to them to show verifiable proof, not us. We’ve literally thousands of tons of evidence supporting our understanding of what led to us. They have zero, and the gray stuff between their ears doesn't count