There is no way to assess why you are as wealthy as you are (or un-wealthy) without knowing your story. Many people know the Bill Gates story. He had a special insight, a drive to succeed, and a will to work hard to achieve his vision.
That doesn't exactly explain why he has more money than you. It just explains, to some extent, why Gates is as wealthy as he is.
Bill Gates took advantage of the right opportunity at the right time. First of all, he had intelligence and inventive skills. Second of all, he was able to recognize and act on an opportunity when it came his way. The two are powerful skills when combined.
Oh I don't know. It could be that Bill Gates got in on the ground floor of a business service that went global. It could be that after he made his initial fortune off of the new burgeoning service that he reinvested his money into new product development and improving the business plan. It could be that he hires people who are able to research business trends and consumer purchase trends to better develop the products his company makes. It could be that what goes around, comes around, and he, his wife, their foundation donates millions of dollars to charity a year. Or it could be that he sees something and goes out and makes it happen. Whatever the reason, he has made a huge financial success of his life.
Bill Gates is one of the richest men in the world. So, he is not only richer than you, but practically everybody else. Part of the reason is that he is certainly a remarkable man with incredible drive. In addition, he was at the right place at the right time. There are some variables that are completely our of our control. For example, what if Bill Gates was born in a poor third world country with no access to computers? I highly doubt he would be rich. So, there is an element of luck or if you are religious, God plays a role. In any case, there are always to factors that make a person great. First, there is timing. Second, there is the ability of the person.
Keep in mind that economics can not fully explain individual-level phenomena. The discrepancy between the two of you may just be because of luck, or because you're lazy, or something that can't be accounted for in economics.
Economically speaking, though, the likely explanation is that he has skills that are rarer and/or in more demand than yours. The laws of supply and demand say that prices are high for things that have either low supply and/or high demand.
Basically, not many people have the ability to invent a whole new technology (the supply of people with his ability is very low). Also, it was a technology that a lot of people wanted (high demand). So he got rich.
But give yourself time -- he wasn't rich at your age either.
People become rich in many different ways like being born rich, winning a sweep-stake, being lucky to stumble upon a big hidden treasure, or by earning the money.
I do not know how much money you have or how you got it. But as far as Bill Gates is concerned, he has earned all the money he has by using his technical, management and business capabilities to create and sell useful service and products that people find useful.
No doubt that Bill Gates has earned a lot of money, but this money has not been accumulated by depriving someone else of anything. As a matter of fact the the combined benefits enjoyed by the people who use products sold by Microsoft, the company set up and run by Bill Gate, and the money earned by people working for Microsoft, is likely to be much more than the money earned by Bill Gates.
In short, we can say that Bill Gates has become very rich by creating enormous value for others, and in the process earning a part of that value for himself.