If you have a boatload of money to spend then the i7 5960X is beyond overkill for gaming. So yes it's very very good for gaming.
But, keep in mind it's lower frequencies will make the i7 4790k and 6700K faster than itself since most games rely on faster single cores. Overclock at least 4 of those cores to 4.5ghz to get the best performance for gaming out of it.