[2Cor4:3] If the gospel is hidden, it is to those who are lost (this actually being a mercy, because 'to whom much is given, much is required' therefore, there would be less punishment for those who never heard, then for those who heard and turned away).
However, I don't think this necessarily applies to some people who die young or people who go into a "vegative state". We might need someone to be physically conscious/alert in order to communicate and interact with them in a meaningful way- but God doesn't. We have little in the way of knowing about what is going on with people in altered states of consciousness. But we can be assured that God knows what he is doing, even if we don't understand what is going on.
Yes, it's a choice. Calvinism et al. is wrong.
It really comes down to self-preservation, too: you will see the argument that "the carnal man would not choose to repent, because the wisdom of god is foolishness to them... blah, blah, blah" <<-- wrong. The carnal man knows self-preservation, and all someone needs to choose repentance is to know that if they don't repent, they will be utterly destroyed. The Holy Ghost was given to help people actually follow through with 'bearing fruits meet for repentance', but the choice to repent was always the person's choice.