Which, right there, shows that the types aren't balanced against each other. But they really don't have to be unlike character races or character classes. Type is just a building block for monsters and races, just like abilities. You don't really ask if an elf's lowlight vision is balanced compared to a dwarf's stonecunning. Rather, you look at the whole package.
There are of course points where the relative balance of creature types can come into play, such as templates that grant those types and their benefits. But those tend to grant the more powerful types, and are presumably balanced with that in mind.