Apart from other more deep issues like code, decentralization & even ideology (for some), indeed only Bitcoin serves as a tender when it comes to buying stuff and not only online. Other cryptos (well most of them) are pure speculation and that's why they are useless in the real world.
The spark behind bitcoin's usability came when a guy gave 10.000
BTC for 2 pizzas, after that point people just started exchanging stuff for bitcoin and fast forward to today you can buy some 333 pizzas with a single Bitcoin