that is a common mistake and you are being brainwashed by the altcoin advertisers/bag holders into thinking that is true.
the fact it bitcoin being big has nothing to do with it being first. being first surely helped but the reason why nothing has yet come even close to bitcoin is because they either copy bitcoin's code/technology or they create something useless with a lot of problems while trying to fix a small and simple problem that bitcoin has.
if some day someone creates something that is REALLY good not just looks good then it will come close to bitcoin and it can even grow bigger than it. but such coin is not yet created and may not be created unless altcoin devs and the community stop wanting pump and dumps.