My definition of "God" would be "intelligent entity that created the Universe". If the Universe is a simulation, then whoever created that simulation is God from our point of view.
Okay, but That excludes
most of the characteristics of
most of the religious conceptions of god(s). Personally I'd regard it as a rather bizarre and pointless relabelling of something that might be entirely flawed and mortal and even have what we might regard as morally questionable motives. It's also pretty much a dead end. There
might be such an entity (or group of entities) but there isn't any particularly good reason to think so (the SU argument isn't all that convincing although it's somewhat better than the traditional arguments for god) and if there is, so what? It's too vague a definition to take any further.
Also, perhaps you could answer the question that Vlad's been studiously ignoring? Just how much of a universe, and to what degree of detail, does a simulation need to be and have before its creator earns the label 'God'? If we take the SU argument, then, on the way to a full-blown simulation of a full universe (even if that was ever the aim), it's likely that a simulator would start somewhat smaller, perhaps with just a planet, or even just a single brain (perhaps not even a human brain) simulated in any detail, while all the rest is only simulated well enough to support the object of interest. Or is this more general; if I write a
Game of Life implementation, am I the 'God' of that 'universe'?