What would make me accept the existence of a deity?

[Angrboda]

If everyone got a god broadcast into their minds every morning would you all nitpick and be so dogmatic about it? If it did happen I would have to accept that as plausible positive evidence.

Absolutely I would. I can think of too many ways one might duplicate many of God's supposed powers with sufficiently advanced technology. And I am not going to worship anybody just because he has better toys than I do. Someone from the Middle Ages might think I am God, or something close to it, because of the things I could do with access to modern technology.

Why shouldn't we be skeptical?

How does one judge whether something is a god if not by the effects? What criteria would "rule in" a god? It sounds like you would rule out any and all potential gods. If they have a method, their godhood is technological and not real; if they have no method, you eliminate the hypothesis as being an argument from ignorance. It sounds like you've rigged the game so that no god can possibly win. That seems to make your disbelief as irrational as the belief of those who accept a god based on too little evidence.