What percentage of grizzly and polar bear genes are the same?

Answer 1

A lot, because they have been known to hybridize:
http://news.nationalgeographic.com/news/2006/05/bear-hybrid-photo.html

It looks like polar bears are an offshoot of brown (grizzly) bears that have about 99.3% of the same mtDNA. One could make the case that polar bears are not a different species from brown bears, since they are contained within a lineage of brown bears found on certain southern Alaskan islands.

Answer 2

All bears and humans have roughly the same genes because we are all related in time.