For at least a decade, Apple has mostly been the company that makes the iPhone. Obviously, it makes other products, but none of them are the reason Apple is a $2.5 trillion company. The iPhone isn't just Apple's most important product, it's the device all other smartphones are measured against.Despite that, Apple's biggest hit product right now isn't the iPhone--it's the Mac. You would be forgiven for not seeing that coming. In some ways, you could argue that the Mac, as it exists today, is Apple's biggest hit. At least, it is right now.