It depends... which god?

"You suck at this"

your replacement has arrived.

I would say "so your that bastard that's responsibile for all the crap that is going in this world"?

You got some s'plaining to do.

Well I'll be damned.

I would ask him why he allows so much needless suffering to be focused on people that don't deserve it and allows so many horrible people to experience success and have influence.

Can't beat Stephen Fry's response. Some good additions here already, though.

Me? I'd ask him why, when a man rapes his 12 year old daughter, he sometimes pushes that big old 'make a baby' button of his. If he has the power over conception, and every new life is his will and blessing, why does he burden any 12 year old with that? Especially one that's been a victim of their own parent.

Indeed, why does he press that button for people who can't afford to raise their children or won't care for them, and staunchly refuse to press it for well off couples who would dote on their child?

Anyone would think that he just stabbed at that button at random. Or that he and the button didn't exist in the first place.

“What the fuck!? You’re fired!”

"Beg humanity for forgiveness."

In my defense, I was skeptical and really high and severely unloved. Also, what's up with my being transgender? Did you like, make a mistake or something? It's ok, I forgive you I guess.

I would ask "Why did you allow SO much suffering, especially to innocent children who were abused or starved to death?"

"I've always done my best to be kind to other people within my limited means; what's your excuse you egotistical, all powerful bastard?"

I would ask, why is everyone I know more moral than you.
Everyone I know would stop murder, rape, assault, famine, why won't you?

If I had only one question?
Why must there be suffering? How does it serve anyone or anything? Why do you allow it to continue.
And if he gives me the freewill dodge I would punch him in the face.

I would say"Oops...my bad... you've done a pretty horrific job at this... would you like some help? And some wine?

Damn! This acid is GOOD!

Pretty lousy job you're doing.

Him???? I plan to be dead when I have died. None o this magical thinking . I reserve my magical thinking for elves, fairies and dragons. This gives me a chance to post my favorite quote:
“Do not meddle in the affairs of dragons for you are crunchy and taste good with ketchup.”

Gang rape? Why'd ya think that was a good idea? The bystander effect? Children with cancer? Anybody with cancer for that matter? The elections of 2000 and 2016. Dead 6 million Jews. Why? People spending their entire lives in prison for crimes they did not do. Shame on you.

Depends which god I suppose.

Where the hell have you been?

Id tell him he should be on his knees apologizing to everyone he killed with a natural disaster or by terminal illnesses or something like starvation.

Or her?

I wouldn't say much of anything. I don't interact with terrorists.