We can say, bitcoin is much better in terms of investment return but we can't say that it could be better for a long term investment. Just because of bitcoin's price volatility compared to real estate and stock. Though they have also chances of price inflation anytime but it is only of less percentage compared to bitcoin.
I agree stocks and real state can assure your money for the next 20 years however in terms of bitcoin if you're gonna think long term you will never know if the price will still continue to increase within the said amount of years , bitcoin is good for short term investment like 2-5 years however if were gonna look more than that we really cant assure if the price will continue to increase just like what bitcoin is doing today