Only bitcoin and real estate are assets with fixed supply. Meanwhile, gold is a finite resource and the supply of gold is increasing every year thanks to mining, recycling and the discovery of new gold mines.
Also, pay attention to their demand, supply is not the only deciding factor. Like gold, no matter how much the supply of gold increases, the price of gold will never decrease because the demand for gold is so great that it will never be saturated.
Of these three assets, bitcoin is the newest and most volatile, or arguably the riskiest. With such characteristics, bitcoin is more suitable for investment purposes than for use as a savings tool. A good savings instrument must meet the criteria of safety and stability, not be a volatile asset.
To be fair, oil, gas, gold, silver, these are "finite" as well. Just because we are unearthing it, doesn't mean they are unlimited, the whole world has a very limited number of gold in it. There is just 20% of the total supply that is undiscovered so far by estimates, and that means we are not going to see that many gold to come out anymore. Others are less, like silver has more to mine etc, or oil, there is still some time until we run out of oil.
BUT we will run out, it is not something that is infinite, you have to remember, even if the WHOLE world was made of gold, it would still be finite, not non-finite, and that's important to realize. Gold is limited supply, it is just that we are not seeing it as valuable as we used to, because it is not a currency anymore, just an asset.