What is the difference between "genetic" and "hereditary"?
From dictionnary.com


  Genetic:
  pertaining or according to genetics
  
  Hereditary:
  passing, or capable of passing, naturally from parent to offspring through the genes:


Note: I selected the pieces of definitions that I found most relevant to the current discussion.

Genetic information can be passed on to offspring. As such, I understand the confusion you may have.

When the adjective "hereditary" does not apply

By its definition the adjective "genetic" can be used in multiple situations where the adjective "hereditary" could not. It is specifically obvious when the term "genetic" is used in the context of a whole population. Indeed, not all genetic patterns are inherited especially when referring to population-wide patterns. Also, the adjective "genetic" focuses on genetics and not necessarily on its characteristic of being inherited.

Example

Consider for example the concept of "Genetic signature of selection". A genetic signature of selection is any pattern in the genetics of a population that can be used to infer past selection invent. These patterns include
 - high population divergence around the specific site
 - loss of heterozygosity (and polymorphism) around the selected site
 - modification of the site-frequency spectrum
 - genetic - environment covariance

Further information

Please note that the concept of heritability might have an unexpected definition for some layman. You might want to read Why is a heritability coefficient not an index of “how genetic” something is?.

When the adjective "genetic" does not apply

There are non-genetic information that can be transmitted from parents to offspring (or even between unrelated individuals).

Examples

Niche construction inheritance or epigenetic (esp. in the broad sense) modifications are examples of non-genetic inheritance.

Further information

You will get more information about non-genetic inheritance (and its role in evolution) in this answer.