Wouldn't that make Aramco the most valuable company in the world?
Apple's market value (just like other such companies in the list like Microsoft or Google) is pure speculation (let alone Buffett's Berkshire Hathaway which is third in the list and only marginally cheaper than Exxon Mobil, by the way)
Aramco is largest company probably if you value the reserve assets. All of the largest companies are national or not public. Aramco might be cheap at its price because of doubts on control I guess, it may rise quite well after listing as hopes speculate upwards or the oil price goes up
Apple does not produce the goods really but owns the rights to each design. It cant be called pure speculation because of that, some people may prefer raw assets but this also is not real value until sold. Presuming the Saudi oil is all real and as easy to extract then the value of that company is larger then every other oil company on earth, the listed ones anyway
Berkshire owns real business, thats the majority of its holdings I think. He also deals in contracts and insurance of course and more virtual profits but Warren Buffet is very much interested in real productive business. Its just he buys other peoples or large shares in them like Coke and he is their largest owner, he is given a free coke machine and free stock though the company is massive and BRK is not the controller. None of thats speculative apart from the normal price in every share presuming future earnings, thats just investment.
He also owns an oil company and a rail company maybe 10% of IBM not sure but any larger owner is public record and nothing he does is that small afaik