https://i.imgur.com/AltAcnB.jpg
Keep in mind this graph is logarithmic in scale.
If I take that same money and invest it in a business -- the business is going to take that money and create something new. Hopefully what it creates will be worth more than what you invested, but in any case your investment has changed the world in some way.
I think a cryptocurrency is probably something in between that, because your 'investment' is actually ultimately going to miners who will expand the network, so you are actually building something new in a sense by investing in cryptocurrency. However I'm not sure that building the bitcoin network out is a net positive for the world.
Only if you're buying at the IPO. Most of the time, you're just buying stock from another person and the company gets zilch. The service you're providing to the company is just better information about its ability to raise additional capital from selling equity.
For some cryptocurrencies, you are providing a service to the miners by adding liquidity and pricing information, but given the volume trading on crypto exchanges, there is simply not enough currency being mined for even a tiny fraction of it to be going directly to miners as a counterparty. For a currency like Ripple, that is completely pre-mined, you don't even have that.
However, over a long enough timeframe storage fees eat up the entire value of gold stored thus it's not a long term investment.
Also, if you 1 one bitcoin you can only sell less than 1 bitcoin from transaction fees. Remember, someone needs to spend real money maintain servers and that money is constantly being removed from the coin ecosystem.
If I own a house I get to use the house today and still have a house tomorrow. With a field I could grow crops and then still have a field next year.
Commodities are an interesting 3rd thing. But, closer to buying something from a wholesaler than an investment as they represent actual goods (ie Oil) that will be sent somewhere. Think of it like this, if you buy coffee contract you get coffee which can be sold off. However it's a physical thing and it's got a physical expiration date, if you keep it in a pile somewhere for 10 years you end up with dirt.
You could speculate that the utility created will increase the value of the coins you hold. However, unlike mining there is no connection between buying a coin and enabling other people to do these transactions.