I don't know. I think 'I'm fine' is quite a decent response under most circumstances. :p
Most people don't push back against it as being okay, good, fine... is the norm. Anything outside of the norm typically receives a negative response. And who really wants to say that they aren't okay? That something is wrong or that they need help? Burden another with what is supposed to be 'their problems'?
*sigh* Am I really saying this... fuck it... i guess... Also, color of the background for those who wanna.Is it right? Situationally... depending on the people, time, and other small things that play a role in how we decide to do things. But I guess the question becomes:
Do you push and try to get someone to open up when you know something is wrong?