Gold and silver yes. Diamonds no. Some things are scarce while others are artificially scarce. What people don't understand about Bitcoin is where it derives its value from. Firstly it is belief, without belief in it there would be no underlying value. Network effect is another big reason it has perceived value as its use in everyday life cannot be denied. Finally you have the energy it takes to secure the network and mine it. I would argue that Bitcoin has more true underlying value at the moment than diamonds but Gold and Silver are hard to beat!