Unless that mind control allows a saving throw, it’s not fair to call someone a credulous fool for having their mind controlled by alien technology. Of course someone mind controlled into believing in god will believe in god. That’s a tautology.
Given the limited definition in the OP (that is, God is the creator of the universe, not necessarily an omni-anything critter), I’d evaluate that hypothesis just like any other hypothesis. In other words, is it the best available explanation for the available data? Do its implied predictions bear out? Can I falsify it?
Assuming that it fits these criteria, then I’d accept that I’d encountered evidence of a creator of the universe. By the OP’s definition, right now I guess the Big Bang is God.
Other stuff–miracles, walking talking icecreamcrapping tacos, history lessons–would be totally irrelevant to the claim that I’d encountered the creator of the universe. There’s no particular reason that a particular rockyroadshitter would happen to be the Creator.
If you make other claims for God, I’d expect to see evidence in similar proportions. The more grandiose the claim, the more grandiose the evidence has to be. For example, if you claim that your god can move stars around at will, I will evaluate that claim based on evidence that your god can move stars around at will; I won’t just accept it on faith.
If you make the supremely grandiose claim that an entity is omnipotent, the evidence must be equally grandiose. I suspect that, just as omnipotence is beyond my understanding, the evidence itself would be beyond my understanding; I’m not sure I would be qualified to evaluate a claim of omnipotence.
But changing my atheist mind wouldn’t necessarily mean making me a believer; you could much more easily change my mind by moving me toward the believing end of agnosticism. If, for example, each night the stars reconfigured themselves so that everyone saw “Love one another, you bastards!” written in the heaven in their own native tongue (and those who couldn’t read nevertheless could read this message), and if conversations and observations through multiple channels consistently verified this finding, I’d find myself moving much closer toward being religious. If someone appeared who explained how to make the world a place devoid of suffering, the problem addressed by theodicy would disappear, and I’d become much closer to being a believer. Various incredible things could happen for which God would suddenly become a plausible explanation, if not necessarily the only plausible explanation.
Daniel