I don't think you can say both Bitcoin and Gold will both be a good long term investment. If Gold will be a good long term investment,then Bitcoin will be a VERY good long term investment, because the potential upside for Bitcoin is way bigger than it is for Gold which already got a multi trilion dollar marketcap. With a $100,000 BTC investment right now, you will most likely change your life and retire in 5 to 10 years.
Now, if you are holding $100,000 worth of gold... you aren't most likely going to do much when it comes to changing your life.
This is simple risk and reward. Gold may be the safer investment, but you can't say the rewards will be the same.
But gold isn't a good long-term investment simply for its potential upside, but because it is a safe haven - recognised everywhere and by everyone to be a sure bet. Sure, it's under pressure now and for the next few years from crypto, but even a decade can be considered short-term when talking about it in this frame. You can confidently lock in gold for the next 5, 10, 25 years. As much as I'm gung-ho on crypto, I can't find the same confidence for where it'll be a year from now.
Of course > risk, > reward... but generally you want long-term investments to be low risk.