If I were to compare bitcoin side-by-side with other cryptocurrencies, I would find advantages and disadvantages of both. Bitcoin has several advantages, including its security, network and market size; compared with other cryptos it is the least volatile. I argue that the lack of a figurehead and the necessity for near universal agreement to code updates is an advantage worth having in a ideally largely non-speculative currency. But the only advantages that actually matter, are the fact that it was first and it can be updated.
First move has a small advantage in most markets, but to the general public composed of unsavvy investors, it means everything. Investors risk in calculated amounts as speculators in markets, betting companies over others. In the traditional market, first move only carries a small advantage. But when the general public are meant to use and therefore invest in a market of currencies, the first move means everything, especially if the market is adaptable and evolving without the general public's necessity to act. This means once they are in, they are probably in it for the long haul, as unsavvy day-trading can lead to substantial losses.
It's true that much of the general public haven't invested in cryptocurrencies yet, but for almost 10 years, bitcoin has led the way. It didn't just explode onto the speculative scene 6 months ago, it's been slowly gaining loyal users for 10 years. It's a brand that even those on the sidelines watch. All eyes are on it, and if it fails, the ripple through the cryptocurrency market will be felt for years, probably a decade or longer.
But it won't fail, because it can be updated by anyone, and the update has to be nearly unanimous. Anything any other cryptocurrency can do, bitcoin can do, and will do with a larger market and more secure and stable network. Even the less secure turing-complete model Ethereum has can be built onto the more secure stacked code, enabling all the advantages with a minimization of the disadvantages.
As there is little market value with unlimited supplies, there must only be a scarce supply of cryptocurrencies. There is no reason for the vast majority of cryptos other than as real world testcoins, and because bitcoin has been around for so long as the leader, with the majority of other coins gaining popularity only through bitcoin's popularity, bitcoin will stay the leader.