[akvadrako]

I would say you have to start by defining "real". Surely a simulation is real in the sense that it takes up physical resources, has to be internally consistent and other such criteria. Importantly, abstractions within it can have experiences that are just as meaningful as those outside.

Maybe it's about being a "top-level" universe, which is self-defining and without physical constraints? It seems ours is unlikely that if inflation theory pans out, instead being just a self-contained world in the multiverse, not so different than any other simulation.

Personally, but without much evidence, I suspect there are no top-level universes; perhaps they do cycle around though, so very large scales eventually become the very small.