The next investment after Bitcoin seems to me to be real estate. If a person is able to do proper research and make the right decision, then his chances of profiting from real estate are much higher. However, each person has the right to make his own decision and each person can proceed according to that decision.
If I consider my personal decision, then I will definitely put Bitcoin above all and along with this I will invest in another field or start a business. I have a dream for a long time that I will start a business and I cannot start because I do not have enough money to build that business, but I will start very soon and move forward with everything together, especially Bitcoin.
The emphasis is not on profitability for now, we are talking about a high value asset that can easily be verified. I don't think that any other asset comes close to Bitcoin. You do not need help from anyone to verify transactions and the details you need to know, the blockchain can be accessed by everyone anytime or day and with ease.
But when you need to verify some information about the real estate investment, you may have to go through agents, to scanning through documents, asking questions, getting approvals if there is need for it. No other asset comes close to Bitcoin.