If you can go back with time, there are a lot of altcoins that are only temporary and they are only driven by hype every time there's a bull market happening. This list is the newest altcoins that pop.
During a bull market, it's possible that new projects could rise in popularity and overtake the positions of current top 20 projects.
It's already proven, only Ethereum since the beginning is always on the top, that's the only altcoin I can trust right now.
Yes Ethereum is an altcoin without a doubt and certainly much more stable,
those are things that usually happen when the market is bullish so we have to be careful,
apart from Ethereum coins like BNB are also trustworthy coins
Having trustworthy projects like eth and bnb would make sure that not only you will go up, but you will go up more than bitcoin probably. Not by a lot of course, but in a world where bitcoin goes up x5, eth could go up x6 and bnb could go up x7 which is not a huge difference, but it's still not a bad one at all.
It's also smart to diversify your portfolio, that way you would make a good profit while also protecting your portfolio in case anything happens to just one of them. Not likely that it would be any big trouble for these big three, but if you could also spend a little bit on other small stuff, just like %10 or so, that would be protecting you at least.