like majority says it is Ethereum or Defi based coins because those are on the pick days now.
In the current situation theres no best altcoin to invest in, better to follow the flow, invest on defi projects where the hype is. If you want to invest in a coin better to make research about that coin.
I think now there's have best altcoins to invest for me is ethereum as far as I know and I think many people it is more powrful and portential coins in the crypto world as of now. But they have altcoins who is also good to invest don't look only to the best altcoins but also to the potential as many as altcoins you invest the more chances that you will get a good profit.