This is not an answer, because that reply has lost all meaning in regards to the question, "How's it going?"
If things are actually going really well for you, I deem your reply of "good" to be "about the same as every other day."
And if you're actually going through a rough time right now, I'm already walking past you and getting out of earshot as you're trying to think of a one-word response that accurately depicts your current emotional state, and instead you just let out a, "Good."
So, here's what I'm looking for. Short, realistic answers to the question of "How's it going?" that will force people to either follow up or realize that it's a bad greeting in the first place.