Bitcoin is referred to as a digital GOLD because of its value. But for me, bitcoin is a digital currency. We used bitcoin to promote the fastest way or method of transaction as possible. Besides, bitcoin has surpassed the value of digital gold either or it is an asset that can be used as an online payment transaction these days. Technically speaking,we cannot know the cap of gold so we can't really compare it to bitcoin.
Hypothetically, we can compare bitcoin to gold even in terms of scarcity. The maximum supply of bitcoin is set to 21000000 and this number cannot be changed without consensus. Very unlikely to happen, I believe, except that most of the participants, especially those who hold bitcoin since the beginning, suddenly decide to become poorer. In contrast to bitcoin, gold has unlimited supply. As humanity improves technology, it becomes possible to mine gold almost everywhere, outside the Earth. Gold can be mined on other planets, asteroids, comets, etc. We don't know exactly how much of it out there. But the part of the reason why gold is less scarce than bitcoin is because we don't need to come to consensus to start mining in space. If small group of people were to decide to make money this way (by printing gold) we wouldn't be able to do anything about it.