In Christianity, the law of the Old Testament no longer applies, because it has already been fulfilled. The law was intended to be a way to gain forgiveness of your sins. But Jesus Christ died on the cross to pay for the sins of all. So there is no longer a necessity for the sacrifices and whatnot that was done back then; Jesus already died for you. All you must do is accept Jesus' sacrifice and your sins will be forgiven. So yes, all of those laws about sacrifice and whatnot were "superseded" by Jesus. But not because of his teachings. It was because of his sacrifice.

Think of it this way. Before Jesus, people had to offer a sacrifice to God as payment for their sins. Jesus came and died on the cross to be that sacrifice, but for everyone and every sin. All sins are payed in blood, but now they can be payed for with Jesus' blood. This is why you'll often hear churches talking about the blood of Christ and whatnot. 

Bolded: Correct. That would be true of any time, and of any person except for Jesus. But again, in Christianity, to be saved, you must accept Jesus Christ as your savior. That's literally it. 

@OP: 

If God created the universe and everything in it, it seems perfectly reasonable that a supreme being capable of such a feat would ask (or demand, depending on how you see it) for worship. After all, if God created everything, including us, then we owe him everything. 

You could say that God is asking for recognition of what he created. When people refuse to worship him, then they discredit his achievement. I'd be pretty insulted if someone used what I made for them and then insulted and berated me. 

Oh dear.  I fear you have some grave misconceptions of God.  He loves us like a father.  Which father would not want the love of his children?  God is perfectly holy, perfectly just, and perfectly loving.  He does no wrong.  He has no weakness.  And he loves us.  Is the worship of God necessary?

Suppose that a God of infinite knowledge and understanding created us.  Now suppose that we are created for some purpose.  Would God not know that purpose better than us?  Certainly, he would.  Suppose that we resist what we were made for.  Shall we not end up with no purpose?  Suppose that God is omniscient, omnipotent, perfect, just, holy, loving.  Would we not want such a God in our life?  And if God is the only one with these characteristics, where else will we find such value?

But these are all suppositions.  You can suppose differently.  You don't have to affirm that these suppositions hold any truth.  You can affirm that we have a malevolent, evil creator who wants nothing but evil for us.

Also, THE1, you mentioned something about deserving God's mercy.

...what?

The concept doesn't even make sense to me.  We can never deserve mercy.  Nobody deserves mercy.  Mercy is always freely given.  A silly but common misconception of mercy.  Have you ever given somebody mercy?  It is a gift.  It is unfortunate and sad when somebody takes mercy without understanding the gift you have given them.

Now of course, God gives mercy to anybody who wants it, so I am not even sure why we are upset that God won't give it to everybody.  After all, wouldn't it be rude of God to give somebody mercy when they will not accept it?  If somebody would rather bear the wrath of God, shall he instead give them mercy?  No, God will give them wrath instead.  Don't you realize that when you hate God because of his just wrath that you are in essence refusing his forgiveness?  And if you refuse his forgiveness and mercy, and hate him for his wrath, which you so rightly deserve, are you not only acknowledging his wrath?  Have you not put yourself above his mercy and Grace?  On your birthday, if you refuse a gift from your parent, will they make you have it?  No - but they will likely be sore displeased with you.  But they will forgive you.  And if you refuse forgiveness for the rest of your life?  You have then cut yourself off from the good things of your parents.  The same is true of God.

That would mean God also created the reason that my hypothetical wife passed away recently. Should I be grateful that he makes my hypothetiical life a living hell?

He also created some people who were born to live under horrific circumstances throughout their lives, should I be grateful for that to?

If God created everything, then he is not fair at all. Not. One. Bit. (to quote the Joker :P )

Anyway, let's say that God did create Earth, but not everything that happens on it (something I believe and hope you were assuming in your post). What he made in that case was not automatical happiness (to be grateful about), but a tool for me to use as I wish. If I use this tool to spread nothing but love and happiness (though choose not to believe in the existence of God), do the people who received my love owe God or me anything? What's more important; the guy who invented the tool, or the guy who chose to use the tool for a good cause? And would the good cause not be valid since I chose not to believe in God during the process?

Please, answer those questions.

Why do people bother going to Church then? The moral teachings are not needed (you can ignore almost all of them) and the act of worship only needs to be accepting him as your savior?

Is playing video games really necessary?

Is doing anything other than the minimum requirements to live necessary?

People will fill the voids in their lives with whatever they feel is best. So if someone wants to worhsip god to make themselves feel more complete, then that is their choice.

I know, and I perfectly respect that. This thread is absolutely not about bashing people who worship God. It's purely philosophical,

How does someone who is perfect and everything "need" anything else but Himself? God is not a man/woman to feel needs.

Maybe you should rethink your view on why He guided Abraham - He does know everything doesn`t He?  Someone who is only good can not do evil. That`s what was shown with Jesus death, for example. Only God was pure to saves us, and, why would God, who doesn`t "need" us, save us, if not out of love?

A great post.

Does he? In that case, he knew about every single person who would go to hell before they ever did. He also knew about every single person who would go through nothing but pain throughout their entire lives.

If he truly knew about those people... Would it not be cruel to decide to create them in the first place?

Certainly. 

FIrst, in the beginning, everything was perfect. Adam and Eve were in the Garden of Eden. They had anything they could ever want, and they had the most intimate relationship with God that any person on this planet has ever had, aside from Jesus. God did not want to force Adam and Even to love him, however, and so he gave humanity free will. But for there to truly be free will, there had to be an option for people to not choose God. And so he placed the Tree of Knowledge in the garden, and forbade Adam and Eve from eating its fruit. This was fine, until Satan came in and convinced Eve to doubt God's word and eat the fruit. This was the first sin.

Because of this, humanity was cast out of the garden. This wasn't done to be mean, but to keep Adam and Eve from eating from the Tree of Life... and to keep them from living forever in sin. The punishment for sin is death, and if you cannot die and are sinful, you can't ever be freed from your sin. 

The reason that your hypothetical wife passed away is because she was a sinner. Eve committed the first sin, and spread that sin to Adam (Adam is at fault for his sins; don't get me wrong. He made the choice to accept the fruit), and so because of the nature of a sin (that it spreads to others), all humans are sinners. It is because we are sinners that we have the world in which we live. All of the evil and horrible things you see could have been avoided had Adam and Even chosen better. At the same time, while sin originated from one place, there is also a way to have your sins forgiven through one place, and through that you can gain eternal life. This, I would assume, is something like what you saw in the Garden of Eden. 

On the contrary, God is very fair. To me, it seems that the Christian God loves humanity so much that he won't take away our freedom to choose how we live our lives. He has also offered a path that will lead to an eternal and sinless life. That seems more than fair, actually. Humanity by all accounts does not deserve to be forgiven of sin, yet he gave us the chance to be forgiven anyway.

To your second part; I am indeed saying that the Christian God is not the cause of everything that happens. He gave humanity free will, and the world in which we live is the world that we have "asked" for through our actions. 

Do people who recieve your love owe God or you anything? Well, my answer is no, but let me explain just what I mean. When I say no, I mean that you are not obligated to return anyone's love. You are not forced to give anything in return. Lets say that you have offered your love and assistance to your child, but your child has laughed at you and said they don't want your help. Well, you were paying for them to go to college, but they refused your help. So you stop paying. You love your child, and you would be delighted to take up that bill again if they would accept it, but you won't force them to.

What's more important; the guy who invented the tool, or the guy who chose to use it for a good cause? Well... I'm not quite sure what you're asking here. Can you please explain what you mean?

Would the good cause not be valid since you chose not to believe in God? No, it would be valid. As would all of the other good deeds you have done, and all of the sins you have committed. And in Christianity, the only path to salvation is to accept Jesus as your savior. God is a perfect being, and humans fall woefully short. No human will ever be good enough in God's eyes, no matter how good the deed. But he offered a path to forgiveness of all sins anyway, because he loves us.

Disclaimer: I'm not actually sure where I stand on religion. I only recently began to study the Bible. I had never cared for religion before, but I felt that I needed to actually study it before I could dismiss it as absurd. So far, I'm hesitant to call it anywhere as absurd as many make it out to be. There are things that I struggle with, but it's been a very interesting experience.