None of them would have existed without bitcoin, but (don't crucify me for this) if bitcoin suddenly went away, other cryptocurrencies could fulfill the currency role that bitcoin had quite easily.  And while those forked coins aren't popular on this forum, it's hard to argue that right now it'd be much easier to buy something with pretty much any coin other than bitcoin. 

Careful with that--there are a lot of scammers trying to sell illicit stuff for bitcoin, and often you have no way of telling whether a site is legit or not.  I'd wait until it's legal in your area, too, but that's just me.