Don't believe all the western propaganda that you hear.
Kim Il-sung and his family are definitely lifted up on a pedestal and they are described as having superhuman abilities, but Korean myths on the creation of the world and Korea are still known in the North. The only people I've ever heard describing the Kims as gods are people who were born in the gulag camps and/or people who are selling a story of how terrible North Korea is.
As far as the North Korean propaganda regarding Kim, they simply started early and small. When the Soviets came to North Korea and installed Kim as the leader, he was described as this big anti-Japanese revolutionary. At best, he was an average anti-Japanese rebel. The Japanese did have a bounty on him, but if you went in to the post office, his wanted poster wouldn't have been on the wall.
After the Korean War, the North Korean propaganda department started working on building Kim up. It's really simple:
you write a textbook about your guy, in this case, Kim Il-sung. In the book you talk about how he led a band of rebels against the Japanese and helped kick them out of Korea.
a few years later, you publish the second edition. In this edition, you make a few updates - Kim led the largest band of rebels, and all the other rebels looked up to them and emulated them. Without Kim, the hated Japanese would still be in Korea.
a few years after that, you publish the third edition. In this edition, after discovering new information, and after finding out that some of Kim's rebels were actually JAPANESE COLLABORATORS who lied about Kim's true record, you make a few more updates. Now you explain how Kim and his rebels liberated the whole of Korea while being hunted every waking minute by the Japanese. The Americans were actually helping the Japanese, and they started the Korean War by invading the North, so Kim had to defeat them too!
This pretty much sums up how Kim Il-sung was built up to be larger than life. With each new textbook, with each new news article, tv show, tale, and rumor about Kim, a new "fact" is introduced. Since everyone knows the basic story (from their school days), adding a new piece to the story is relatively easy - people simply think they forgot that part, or that new information has been found.
Finally, it's really easy to say that the Kim family is the greatest, the best, gods, and whatever else they want to hear when you live in a police surveillance state that will throw you and your entire family into a gulag if you don't say it. North Koreans are not stupid - they are very pragmatic.
For more information on the Kim family and the propaganda about them, check out Under the Loving Care of the Fatherly Leader by Bradley K. Martin. It's a solid book on the Kim family and how they built up their status in North Korea.
They do not tell citizens that Kim Il-Sung created the world. I'm not sure where you're getting that from, but that's not what they say. Things attributed to Kim Il-Sung are that he defeated and drove out the Japanese and the American invaders and established the Korean government and made the nation the most affluent, envied nation in the world. Because they have very little to no contact with the rest of the world, except what the North Korean government allows them, they have no frame of reference with which to question the version of events they're taught. And the people who were born before Kim Il-Sung weren't living in a free nation--they were living in a nation annexed by Imperial Japan, forced to not speak Korean, only Japanese, and living under a pretty rigid, brutal occupation. So when a Korean leader took over, that seemed a positive change--even if it wasn't.
As far as the history North Koreans learn, it is true that the Japanese invaders were driven out, and that Americans do not occupy North Korea, so to that extent, Kim Il-Sung's tale of driving out foreign invaders has a kernel of truth. What's not true are how the Japanese invaders were driven out--it was the US, though the Soviet Union was active in working to do that for just the last couple of days of World War II (having declared war on Japan on August 8, 1945). As such, the Soviets got to occupy half of Korea, and the US occupied the other half. But just as with Germany, the US and USSR were having trouble agreeing on how to govern Korea--under whose sphere of influence would it fall? Then the Soviets, unprovoked, attacked the US forces that were occupying the southern part of the peninsula, so that they could control all of Korea. The Chinese helped them. The US fought back and eventually the two sides fought to a standstill and divided the country in half, roughly where the division was before they'd started fighting. But the people of North Korea are taught that it was the Americans who, unprovoked, attacked North Korea, and it was Kim Il-Sung who beat them back and now South Korea is a hellish place that is just a puppet state of the United States. Hearing only this version of events is very convincing to North Koreans. They know from brutal personal experience that there was an horrific war that killed a large percentage of their population, no family was spared, they just don't know that it was Kim Il-Sung and his allies who started it. When refugees from North Korea learn this in the present day, it's apparently a huge, enormous, staggering shock, that makes them question everything they know. Also keep in mind that until the 1970s, it wasn't entirely clear whether it was better to live in North or South Korea, though North Korea was more affluent than South Korea, plus North Korea had better PR and was quite successful in convincing a lot of people that life was better and freer there than in South Korea (and they concealed the concentration camps and other horrors of North Korea). South Korea was kind of a puppet government of the United States back then, with lots of US troops there, and it was financially struggling. Of course since that time, South Korea has become a global industrial giant, its government has become independent of US interference, and it's become increasingly difficult for the North Korean government to prevent North Koreans from learning that life is a hell of a lot better in South Korea than in North Korea. But the way North Korea is, is all that North Koreans have ever known. They lack even the vocabulary to challenge the government version of events.
I hope you're being hyperbolic; it's not actually taught that Kim Il-Sung "created the world."
It's similar to any figure whose exploits are exaggerated and made into myths over time. It's exacerbated by the fact that the state has control over mass media, and a political incentive to generate a cult of personality around members of the Kim family. Indoctrination is a powerful thing. Also, keep in mind that North Korea has only existed since 1945. Most old people alive in North Korea today were adolescents or younger when Kim Il-Sung came to power. It should also be said that it's dangerous to voice dissent or disagreement with the party line; it's possible not a lot of North Koreans truly believe Kim Il-Sung was born under a rainbow that rained gold or whatever, but saying so might result in the whole family being sent to a prison camp.
The cult of personality that developed around Kim Il-Sung didn't come into full swing until the transition to Kim Jong-Il's rule began. That's when you start to see gigantic bronze statues and propaganda posters of Kim Il-Sung as a god-parent to the Korean people. Before that, stories about Kim Il-Sung had an element of myth to them, as with any public figure, but also a grain of truth. Over time, stories are expanded and embellished, often to absurdity.
People who were already "old" in 1945 didn't need to be brainwashed, because the stories were believable. No matter how vilified North Korea is today, in 1945 Kim Il-Sung was a genuine Korean nationalist with well-meaning ideals for his country and his people. Consider that from 1910-1945, Korea was a Japanese colony, and subject to a rather brutal military rule. Kim Il-Sung fought with anti-Japanese guerilla forces in Manchuria in the 1930s, and was a true believer of the communist ideal. He was a member of the Chinese Communist Party, and trained with the Soviet military. Those factual elements serve as the foundation for later myths like, "Kim Il-Sung founded and led a guerilla army against the Japanese as a teenager!"
Moreover, once he came into power, Kim Il-Sung's North Korea was doing a lot better than the South. While the Americans and newly-formed South Korean authoritarian government were picking up where the Japanese left off, in North Korea the state implemented hugely popular land reforms, mass education, work programs, and infrastructure projects. Previously impoverished peasants were given land to live and work. Previously illiterate peasants were being educated in state schools (and being exposed to a state-approved curriculum). In a sense, the 1945-50 period was a sort of golden age for many North Koreans after decades of harsh colonial rule, and Kim Il-Sung gets the credit for that - whether deserved or not. No brainwashing required.
Sources: Andrei Lankov, The Real North Korea: Life and Politics in the Failed Stalinist Utopia Charles K. Armstrong, The North Korean Revolution, 1945-1950