More expensive, better, worse are comparative adjectives.
Now, when we compare these restaurants with a third restaurant, and this restaurant is way better than the others, we use a superlative adjective to describe it:

As you can see, los Primos is much better than the other two restaurants. It is the top option!

Prices are the least expensive.
Its food is the most delicious.
It has the best service.

These adjectives that indicate that something is the best (or the worst) are called superlatives. Here is how we form them: