A tip is altcoins are only potential at the start of bull run or at the end of bear market. In middle of a bull market or middle of a bear market, you will possibly be rekted by altcoins.
Like so often: it depends
A few days ago I investigated the ATHs of a group of altcoins (those which had no premine, i.e. for example XMR or LTC, but also much smaller coins) and I made an interesting observation.
In the last bull run in 2021, most of them had an ATH or local high (not all of them achieved a new ATH in this run, but some did, or were new) in the first half of 2021, while Bitcoin had its ATH in late 2021.
2021 was however for many reasons an atypical bull run. The BTC evolution could be described almost as a double top, with $65k having been reached already in May, but the top of the bubble only reaching 69k in November. Only very few very established altcoins managed to achieve a new ATH in November. It seems that the late 2021 BTC rally was mainly fueled by recognition as legal tender in El Salvador (a "good news rally") which didn't affect altcoins, and thus they didn't join BTC.
In 2017/18, in contrast, the ATH of most altcoins was reached close to the BTC high or even afterwards (BTC's high was in mid-December, while many alts topped in early January, ETH being the most prominent example, but also others like XMR). I remember that in 2013/14 this was similar: at the end of the bull run which culminated in the $1150-1200 ATH in the case of BTC in early December, there was still a little "sucker's rally" in many altcoins, in some cases reaching new ATHs.
So basically in most bull runs there is a chance of altcoins joining Bitcoin to their highs, and even surpass it. But that's not guaranteed. As already was said in this thread, I agree fully that altcoins, regardless of their age and/or market cap, are much more risky than Bitcoin. And "hypecoins" and "smallcaps" are much more risky too. Even XMR, which was for a long time one of the most stable alts, had its big crash recently.
In comparison to BTC, in addition, altcoins seem to have lower returns across cycles. There are few coins which achieve an ATH in each cycle. Solana, for example, has made phenomenal growth in the last months but is still far away from its ATH from 2021 (of >250$).