Do we get 1/4 of our genes from each grandparent?
I have answered a similar question before: "How many genes do we share with our mother?".

It is not that you "get half your genes" from each parent, and thus a quarter from each grandparent, it is that you inherit the versions of the genes (we all have the 'same' genes).

The method that determines which traits are inherited from each parent by the offspring is known as homologous recombination, and this process is (essentially) random, and thus you end with ~50% of your traits (the alleles of the genes) from each parent, and ~25% from each grandparent, so you are right in this respect.

This is, however, a generalization; due to the chance nature of the recombination it is entirely plausible that you may inherit more traits from one grandparent in comparison to another, but this is unique to each individual (with the exception of course of genetically identical twins).