>It would be unethical to create a simulation in which the simulated beings were sophisticated enough to be self-aware and capable of significant suffering

Well .. is it though?

What if everything is so blissful and boring in the future that people intentionally torture themselves for decades at a time by experiencing "Earth-sim" so that they can build character / enjoy the utopia they've created? Or maybe this simulation is the rehabilitation track for criminals? There are a number of reasons to "suffer" and suffering shouldn't be cast out as unethical because we don't like it in the current context.