Anyone can create their own cryptocurrency, this is a fundamental aspect of such systems: they are open and permission-less, so anyone can participate, whether that be using an already-existing cryptocurrency, or creating a new one of your own.
how can there be any worth in a Bitcoin, if there is the possibility that in five years there are a thousand different Bitcoin like system
As a thought experiment, consider this: instead of talking about cryptocurrency, lets talk about metal. Imagine a society where money comes only in the form of metal coins, and the majority of coins are made from a type of metal called 'coinium'. A lot of people use coinium coins to purchase their daily goods, so there is a great deal of economic activity conducted using the coins, giving them great value.
Now, eventually someone realizes that there is another metal, called 'altium', that can also be used to create coins, and it is extremely similar to coinium in many ways, except for the colour is different, so they are still obviously distinct. Just a couple people start to use altium to conduct their business, but the vast majority still use coinium.
What is the difference between coinium coins, and altium coins? They both accomplish the same goal, are equally as easy to make, but still are distinct since they are obviously different colours. This distinction allows people to differentiate between the two types of coins, and each has its own value.
Likewise, there are already hundreds, if not thousands of 'altcoins', many of which are copies of the bitcoin code base. But just because they are all cryptocurrencies, does not mean they are all absolutely equal. Each network is distinct and separate from the rest, so you cannot send a bitcoin to the litecoin network, or vice versa.
So we can see that there is a distinction between a bitcoin, a litecoin, or any other coin. Each one has it's own network, and price, whereas if every cryptocurrency was equal, than we would expect no difference in price between them. So in practice, we see that there is a discernible difference.