Question: Do you think that people who reject God would choose any differently if the choice were made more explicit (i.e. God actually appears before them and gives them the ultimatum directly)?
ultimately no.
this gets to the heart of the question about hell..
First, by hell I assume you mean the lake of fire, eternal punnishment etc.
The problem people have accepting hell is that they believe people are inherently good. It is hard to accept that a basically good person (by human standards) will suffer eternal fire because they were misguided about which god to worship and pray to. Some even because they were born in the wrong family, or the wrong country and were taught from birth to worship the wrong god etc.
I believe that this view is fundamentally flawed. It is wrong because at a very basic level our view of good and evil, and human nature, is flawed.
First, God is merciful beyond our understanding. Thus I have faith, and confidence that no one who doesn't truly deserve eternal damnation will end up in the lake of fire.
Secondly, the fact is that goodness, just as eternal life, is found only in God. He is its source. On earth we have people from all religions, and all beliefs that are nice, and have some good traits. The reason for that is that here on earth, God gives grace to all people at a basic level. Most of the people alive on earth still carry the image and likeness of God even if they are unsaved, and as such they are capable of good deeds and noble sentiments. It is what theologians frequently call "common grace". God has not totally removed himself from those people. They still receive of his grace on a basic level.
This gives us the impression, when we look at it in human terms, that many people are basically good, without God.
However, the contrary is actually the truth. As those people remove themselves from God, they become worse and worse.
C.S. Lewis talks about this in Mere Christianity. What we do in life prepares us either to be heavenly creatures, or hellish creatures. The more we know God, the more heavenly we become. The more we reject God, the more hellish we become.
The result is that those who fully reject God ultimately become vile evil creatures. People are by nature selfish, often cruel etc, but what we see in every day life here is nothing compared to the true vileness that human beings become when their rejection of God is complete.
The result is, while I'm sure that even the demons and fallen angels lament their punnishment... given a reprive they would do again the very things that damned them in the first place.