I think there can be only few competitors for btc. I won't list them, we can see them in top5 crypto. But I don't really believe in every of them as in the King of crypto.
Countless altcoins were introduced and launched to beat the features of bitcoin, and replace its position, yet, they haven't got the chance of getting the popularity of bitcoin. They can always claim to be the best and better than bitcoin, showing comparison tables, graphs, etc., but their bottleneck is the adoption of their currency. If you talk to a noncrypto user, what cryptocurrency he is familiar with, the first thing he will mention is bitcoin. And if you try to mention all the others, they will be confused of their existence. So I don't think bitcoin will be replaced by any other altcoin in the meantime.