Another flipside of the coin you Christians never want to consider:
If your God exists, you're fucked too.
Let me explain. The Christian God is not "all holy", he's not all just, he's not all-merciful. Those are your natural humanistic values you've applied to God, not the values he holds in the Biblical accounts. In the Bible, his name is Jealous. He's a petty control-freak with a hair-trigger temper and ever changing desires, with an ego so big that he couldn't create a large enough universe to contain it. About the only thing you got right is that he's got a shit-ton of power to fulfill his sadistic desires on a helpless human race.
Ever see that old episode of the Twilight Zone where the god-like kid holds that town hostage and can banish people "to the cornfield." That should give you a taste of what Heaven would be like under the Biblical god. You want to talk about being afraid? The ancient Israelites lived in constant FEAR of angering their demonic desert god, and propaganda aside, his son Jesus wasn't that much different, who instituted the concept of eternal torment in a lake of fire.
If Christianity is true, you all get to spend eternity with this bronze-age petulant tyrant who is all-seeing and all-powerful, along with his hypocritical son who shares these values. You'll have to feign happiness and placate his ever-changing whims to avoid his all-consuming anger. The best scenario is that he simply erases all your personalities and memories and turns you into an eternal worship choir (this is how Heaven is described in Revelation). The worst scenario is the constant fear of being tossed into Hell for displeasing him. It's the ultimate existential nightmare. At least atheists in this scenario have the peace of mind of having their eternities settled. Christians in eternity will have endless chances of screwing up and landing in Hell, and since this is eternity, it will eventually happen. And that's if God doesn't simply issue a worse punishment than Hell. He's omnipotent, so he is capable of doing that should he desire.
And don't cite the New Testament's claims that Christians are eternally saved and will enjoy blissful lives for all eternity. The unoffical message of the entire Bible is that God continually promises nice things to humanity in exchange for his worship, and every single time screws over those that he claims to love the most: Adam, Noah's descendants, Abraham, Moses and the Hebrews, Job, King David, even Jesus. Why do you think Christians will get a better deal than those important figures did? The Bible God will just do what he has always done, shrug his shoulders and blame the victim. "You see I was planning on allowing Christians into Heaven, but then I thought about what sinners they all are and changed my mind." Or he could just change the circumstances of salvation, after all he did it before to the Jews by changing animal sacrifice to accepting Jesus. Say God now says "Only those who submit to being continuously raped by Me and my Son get to spend eternity in Heaven," (after all doesn't Genesis say that the Sons of God found the daughters of mankind to be fair?) or says "Turn over your children and wives. Jesus has that itch again." ('Suffer the little children' and all that). After all, he's God, who is going to hold him to account if he breaks or alters the terms of the agreement? After all He's done it plenty of times before, and absolute power corrupts absolutely. Who are you going to turn to? Jesus? He's God incarnate. The angels? The last time an angel questioned God, he got banished and became Satan.
Heaven will resemble a Bosch painting, with a side of HR Giger.
You better fucking hope that you're wrong and the atheists are right.
