What do believers say when you ask or tell them..

[Ryft]

[So you believe in] a God with a one-size-fits-all plan for salvation? One that simply judges a book by its cover?

Since this is a crude caricature that doesn't reflect what I actually believe, there is nothing here for me to respond to. I have zero interest in answering for beliefs I don't have.

Not so fast there.

The Quranic passages you cited address unbelievers (Kafir) and therefore don't apply to me, since according to Islam I'm included among the "People of the Book" (and therefore Al-Muttaqun, the pious).

"[Those] of the Scripture stand for the right. They recite the Verses of God during the hours of the night, prostrating themselves in prayer; they believe in God and the Last Day; they enjoin Al-Maruf [that which Allah considers good] and forbid Al-Munkar [that which Allah considers bad]; and they hasten in all good works; and they are among the righteous. And whatever good they do, nothing will be rejected of them; for God knows well those who are Al-Muttaqun [the pious]" (3:113-115).

"And there are certainly among the people of the Scripture, Jews and Christians, those who believe in God and in that which has been revealed to you, and in that which has been revealed to them, humbling themselves before God. They do not sell the Verses of God for a little price; for them is a reward with their Lord. Surely God is Swift in account" (3:199).

"Those who believe and those who are Jews and Christians and Sabians, whoever believes in God and the Last Day and do righteous good deeds shall have their reward with their Lord. On them shall be no fear, nor shall they grieve" (2:62).

Those alarming verses about disbelievers, rejecters, Kafir? That's people like atheists, among others. As I said, even if my religion is wrong I'll be all right, given the balance of good works—even under Islam, for I'm Ahl al-Kitab, among the righteous who believe in God, enjoin Al-Maruf, etc., and shall have my reward with my Lord.

You also ruled out the possibility that God isn't real and you wasted valuable time in life praying to an imaginary friend.

Wrong. I addressed that. "My life will not have been a waste, because ... [even if my beliefs were wrong] (i) they were the guiding principle that led to those good works and (ii) in the afterlife it won't ultimately matter anyway." Maybe you think it would be "kind of a drag" but, frankly, what does that have to do with me?

[If Christianity turns out to be false, it is of] No importance to whom?

Anyone. If Christianity is false, will that be of importance to the Atheist who dies? The Wiccan? The Muslim? The Buddhist? The Hindu? Nope. If Christianity is false, will that be of importance to the Christian who dies? Nope, for they lose nothing. If any other religion is true, they enter the afterlife on a balance of good works. If atheism is true, they decompose in their grave, having lived a life of good works on balance.

It is of no importance if Christianity turns out to be false, but of infinite importance if it turns out to be true.

Even granting all of these theories are true, it would not prove, in any context, that a God created the universe ...

Irrelevant to the point I was making, which had nothing to do with identifying God as the creator of the universe. It never ceases to amaze me, the keystrokes some atheists here will waste raising objections to things no one said (like "putting an extra factor in the equation" when nobody in the conversation did any such thing).