If creating a whole universe is possible, then some entity would do it a lot, so there are probably a lot more creations out there than "basement realities", so we're probably in a creation.

This is fine, because the burden of proof is on the theists. But if you find the anthropic argument for the simulation hypothesis good, then that's one more good argument than theism has.

Luckily for the preservation of my atheism, I don't find the 'anthropic argument' for the simulation good. And I put the scare quotes there, because I don't think this is what is usually known as an anthropic argument.