Brief Answer:

There are a lot of different beliefs—as many different beliefs as there are different desires of what people want to believe. However, the process of determining what beliefs are false and which stands above all others in evidential support, becomes much simpler because all beliefs fall into four general types.

Detailed Answer: 

There will be as many different belief systems as there are differences in what people want to believe. As a result, there are a lot of different belief systems. However, all beliefs fall into four general types. 

Because the different beliefs all fall into four general types, this allows for simple validation or invalidation by clear and well-established evidence. This topic is covered in the blogs on worldview comparisons.