The NRA used to do a show on like Saturday afternoons called the Armed Citizen which highlighted one or two (I don't remember which) instances where a citizen with a gun had prevented a crime.
According to the NRA each year in the U.S. gun owners use firearms for protection as frequently as 2.5 million times.
According to the
WWW Gun Defense Clock, every 13 seconds an American firearm owner uses a firearm in defense against a criminal.
While I admit that these people have an incentive to twist the stats in their favor, I also have to admit it does happen.