Star Trek has more historical weight behind it. It more or less created modern scifi fandom. It’s probably so widely beloved because it’s unlike most scifi in that it’s hopeful. It sells you on the idea of a better future where everything could go right, where we can explore space and be chill with everyone. Other scifi franchises sell you on window dressing or a bad future full of the same problems we have now.
People like Star Trek because they want it to be reality in a way that other scifi stuff just doesn’t do.