NOTE: I mention some brands etc, I'm in no way affiliated with, they're just examples and not to be taken as the only choice or the best choice.
I believe steem will be prosperous, even if other cryptocurrencies lose value, fail, end up forgotten, steem will hold its, and probably grow in value, at least in time, when its big enough to stand on its own and not go as much with the whims of traders.
And thats because it has a real use, its not just floating around there in the cyberspace doing nothing or seemingly nothing for the majority, instead it exists more concretely, its existence is more easily grasped by everyone, you interact here, provide value to others, and receive steem for your effort, which you in turn can cash out and use to buy real life things.
Or you can even get a debitcard from a provider that supports it, such as Uquid altcoin card, then you can just pay as you would with your normal bank card/visa/mastercard etc, but instead no hassle, no exchanging etc, just use steem to directly pay for stuff in real life.
The problem with other cryptocurrencies in my opinion is the acquisition and usage of them, its difficult, for now at least. Maybe one day soon you can ask your work to pay you in your preferred currency, that'd be awesome, but until then, I feel Steem is where its at.