In reality the majority of the alt coins do provide something that gives it value, else they wouldn't be a top coin. You can say that some coins provide better tech than Eth, and in that sense Eth should be below them, but Eth was there first and grew its value before those other coins. The people who hold Eth aren't going to submit and say, "Here, I will dump simply so that you can take our position as number two."

A lot of coins can do what Bitcoin does and more, but again, it's all about supply and demand, and people's money.

If this were a household item, where Bitcoin is an object you own, and something better came along, then yeah, you could replace it with that something better.