in my opinion, bitcoin is a good investment for long term.
Anyone who has bought bitcoin since 2009 was in profit after 3 years max. It means even if you buy a top, yu just need to be patient and you'll out perform dollars.
As per my experience, bitcoin is always been a better investment. However, since altcoin gives more returns, we should also not miss the profit in altcoin season but trade with caution . Even a minor dump in bitcoin prices, can make us a big loss in alts so one should use proper stop loss while investing in altcoins.