Part of the problem here is that there's no clear meaning of the word ‘god’ (taking for granted that ‘theism’ and ‘atheism’ are defined in terms of it). I usually identify as ‘secular humanist’ rather than ‘atheist’, mostly because it's more precise, but also because I have seen people define ‘god’ in such a way that I believe that one might well exist. These have all been very vague definitions (more along pantheistic than monotheistic lines), but they're not gratuitous (like defining ‘god’ to mean, say, my nose), and by these lights I'm merely a (weak) agnostic.

In particular, if one defines ‘god’ as a person who created the world, then (depending on exactly what ‘person’ and ‘world’ mean) the simulation hypothesis would indeed imply the existence of a god. You seem to be hinting at this, while other respondents deny it. You all may just be talking about different things. (I will sometimes say, if pressed, that I do not believe in a person who created the world, using precisely those words, but then I don't buy the simulation argument.)

Of course, one can argue over what ‘god’ or ‘atheist’ ought to mean, in order to communicate most effectively with other people. For my part, unless I'm speaking with (or about) a theist whose beliefs I more or less understand, I don't usually use them at all.