Cutting to the meat of the matter...
Let me put it this way: hopefully we can both agree that murder of an innocent person is evil. What would be a just punishment for such a murder?
Whatever you think a just punishment would be, it is finite. You may say that it's good, right and just to make the person suffer horribly for his crime, but at some point, no more suffering is justified. Depending on your personal inclinations, this might be after an hour, a few days, or maybe a decade, but whatever it is, at some point, even the most vengeful person would say "okay - he's had enough".
Now... how bad is the "crime" of following Satan? Is it worse than murder? A hundred times worse? A million? Whatever your answer, the same thing applies: at some point, even if it's after a billion years, we reach a point where justice is satisfied and the person has had the limit of what can be considered a just punishment.
But Hell keeps going. Once justice has been done, the person continues to suffer in torment... over and over and over forever. No matter what awful crime a person commits in life, since human beings are finite creatures, it is a finite crime. But any infinite punishment for a finite crime would, by definition, exceed the limits of what is good, right and just by an infinite amount.
I've heard Christians make excuses for this by saying that Hell is just "separation from God", or that our default situation is suffering and God isn't punishing people so much as failing to reward them, but it seems to me that these explanations wouldn't work for you. The Quran passages you quoted make it clear that in the Quranic view, Hell is a special place specifically created by God expressly for the purpose of inflicting punishment.
But that doesn't really address the key issue in my mind. What you describe only explains that God will do what he said he would do. This doesn't do anything to establish that he's right to do it.
Not really.
Let me address your question from a comprehensive point of view.
I talked about certain assumptions earlier in my previous posts, because i knew that as we go on in the discussion, some answers would require an acknowledgment of certain attributes of God. I won't ask you to assume God is Good because we already agreed that it won't be fruitful, but i'll speak of something else which you are already familiar with.
You know, i can clearly see your point now, and i would certainly have agreed with you that God would appear to be less merciful and less just if he had punished us for something finite.
The *finite* crime which you speak of is NOT finite. God knows our past, present, and future, but he is out of space and time. God said in the Quran that those who will enter hell deserve to be there forever because he KNOWS that even if they have lived forever, they would still be the same. So he is punishing their infinite ever sinning soul, but not only their finite sin on earth.
This issue has not went un-mentioned in the Quran.
27. If thou couldst but see when they are confronted with the Fire! They will say: "Would that we were but sent back! Then would we not reject the signs of our Lord, but would be amongst those who believe!"
28. Yea, in their own (eyes) will become manifest what before they concealed. But if they were returned, they would certainly relapse to the things they were forbidden, for they are indeed liars.
29. And they (sometimes) say: "There is nothing except our life on this earth, and never shall we be raised up again."
30. If thou couldst but see when they are confronted with their Lord! He will say: "Is not this the truth?" They will say: "Yea, by our Lord!" He will say: "Taste ye then the penalty, because ye rejected Faith."
31. Lost indeed are they who treat it as a falsehood that they must meet Allah,- until on a sudden the hour is on them, and they say: "Ah! woe unto us that we took no thought of it"; for they bear their burdens on their backs, and evil indeed are the burdens that they bear?
32. What is the life of this world but play and amusement? But best is the home in the hereafter, for those who are righteous. Will ye not then understand?
(Quran 6:27-32)
Just the same as someone who is facing death, he would say ...
99. (In Falsehood will they be) Until, when death comes to one of them, he says: "O my Lord! send me back (to life),-
100. "In order that I may work righteousness in the things I neglected." - "By no means! It is but a word he says."- Before them is a Partition till the Day they are raised up.
(Quran 23:99-100)
You know, although some analogies are good to start a discussion in religion just to establish a solid ground of understanding, but it fails sometimes to reveal the whole truth.
You can use any type of analogy but the problem is that it will not exceed our human experience. We are very limited because there is no one like God. For example, a judge would punish too, but he can't read people mind or see inside their hearts, so he can't not make some speculations regarding the future of a specific criminal for instance, unlike God, who knows what is in our heart, and he knows what we reveal and what we conceal. God doesn't need to wait for us to sin infinitely to punish us, because he already knows our future, our heart, everything.
So, it's an infinite punishment for an infinite crime.
On the other hand, there are other opinions which might be shared by other Muslims, and one of the opinions about hell is that it won't be eternal, but i disagree with that opinion, that's why i didn't mention it.