"Why all people are not saved?"
I am not sure what you mean. You take a statement & then make it a question but in a form that is difficult to interpret what you mean. Can you please rephrase the question to communicate what you are asking. Thanks.
Now on to your next question. "Is the best answer: “Only God knows & you will have to ask Him when you get to heaven?” No, it isn't the best answer because God has already answered it.
Now on to your third question asked 2 different ways:
"Could God not save anyone & be true to His nature? Could God save everyone & be true to His nature?"
God will be true to His nature, whether someone is saved or not. You are dealing with hypothetical questions that don't deal with reality & with Scripture. Some people ARE SAVED & some people are NOT saved. That is the truth & fact & reality.
Now on to your next section:
"According to some, God could just as easily & righteously save your neighbor as you, so would you be just as happy or even happier if God saved your neighbor instead of you, since you are to Love your neighbor as Christ Loves them? How is this selection method not arbitrary?"
Again you are dealing with a non-reality hypothetical situation that isn't based on truth. And the Scripture is: 'Love your neighbor as you love yourself.' And it is not arbitrary because God has stated the difference between those who are saved & those who are not is belief in Christ to save them as their Lord & Savior. The 'gospel is the power of God for salvation, to everyone who has faith, to the Jew first & also to the Gentile.'
One cannot select one attribute of God to the exclusion of the other attributes of God. All operate harmoniously. So if one says God is the EPITOME of love, to the exclusion of His other attributes, then one is NOT accurately describing the Biblical God. This is a false god. God is the epitome of holiness at the same time God is the epitome of righteousness at the same time God is the epitome of justness at the same time, God is the epitome of love & so on.
It appears as if you have an agenda, for all these hypothetical questions & meanderings. Cutting to the chase, it appears that your real motive is to try & marginalize people going to hell & the real issue is that you are questioning God why He justly casts people into hell (Gehenna) for eternity?
People end up in hell based on their own choices, their own words & actions--coming back to judge them. They are judged based on their own self-righteousness & self-justification & not based upon Christ's death on the cross & the resurrection. They rejected Christ & chose to rebel against a holy & just God.
Romans 9:12-14 In the words of the Scriptures, “I loved Jacob, but I rejected Esau.” What then shall we say? Is God unjust? Certainly not!
2 Chron 19:7 And now, may the fear of the LORD be upon you. Be careful what you do, for with the LORD our God there is NO injustice, partiality, or bribery."
Job 34:10 "Therefore listen to me, you men of understanding. Far be it from God to do wrong, and for the Almighty to act unjustly."
Psalm 92:15 "...proclaim, "The LORD is upright; He is my rock & in Him there is no unrighteousness."
Job 40:8 Would you really annul My justice? Would you condemn Me to justify yourself?
Psalm 51:4 Against You, You only, have I sinned &done what is evil in Your sight, so that You may be proved right when You speak & blameless when You judge.
Romans 7:7,13 What shall we say then?
Is the law sin? God forbid. Nay, I had not known sin, but by the law: for I had not known lust, except the law had said, Thou shalt not covet.
Deut 32:4
He is the Rock, His work
is perfect: for all His ways
are judgment: a God of truth & without iniquity, just & right
is He.
Psalm 7:11 God judges the righteous & God is ANGRY
with the wicked EVERY day.
Romans 3:3-5 Certainly not! Let God be true & every man a liar. As it is written: “So that You may be proved right when You speak & victorious when You judge.”But if our unrighteousness highlights the righteousness of God, what shall we say? That God is unjust to inflict His wrath on us? I am speaking in human terms. Certainly not! In that case, how could God judge the world?
Your hypothetical & convoluted argument based on eisogetical methods of pulling verses out of their contexts, does NOT prove: 'not saving some HAS TO BE to the benefit of others.' It doesn't. God is not benefited because 'He desires all men to be saved & to come to the acknowledgement of the truth...He is not wishing any perish but all come to repentance.'
Others are not benefited, who have prayed for the salvation of this person and/or have shared the gospel with this person. It doesn't benefit the person being cast into hell (gehenna). Yet the basis of the judgment & the wrath is based upon unbelief, not trusting in Christ to save them from the judgment & wrath of God.