I like those kinds of movies, too. And books (which do a better job of telling a story, if not as visually exciting).
Look at the Mad Max movies. OK, its Australia, but people are fighting and killing over the last gasoline, and by the time of the movie setting, there are only a handful of shells left (and some of them have gone bad).
The main bad guy in one of them, who presumably can get the best of whatever his gang can find has a nice scoped S&W, but doesn't even have a full cylinder load of ammo left for it.
I'm sure it would take longer in the US, (we have lots more guns and ammo to begin with), but eventually in a situation like that, the ammo IS going to run out, and the guns become awkward clubs. Which is why those stories always tend heavily to bows and swords. Those can be made, and even made well on a local level.
But back to reality (or something like it...) while we have been "trained" by popular entertainment to expect to have to fight off the hordes, its a much better idea to hide, if you can't run. And better yet is to organize with the people around you. Local militia, or what ever you want to call it.
You can have dozens of guns and thousands of rounds ready for "the day", but if its just you, or just you and your family, you are in trouble if you are found by the a group of the lawless. Even if you drive them off (and killing them all is even more unrealistic) the survivors will know where you are, AND that you have guns and ammo, which they WILL want for themselves. And without enough people on your side, can you hold out until outside forces restore order?
Just how long will it take, anyway? A week? two? In the past century or so, I can't think of any disaster (outside of war) that has taken more than that before some kind of order is restored. Hooking up with some friends/neighbors/co workers, so somebody can keep watch on things 24/7 is a very good idea. Especially if they don't come to you with just empty hands.
I used to work with one of those "7 years of food in the basement" kind of guys. He had a couple, but wasn't really into guns. We worked out a deal that if it came down to it, he would take in me and mine, and feed us, and I'd bring the artillery and ammo to protect his. Figured we'd have some time on our hands, as going to the plant to work in lawless times seemed kind of silly.
Ok, I'm way OT. Sorry. Put aside a few boxes of ammo for your 9mm or .40, or what ever your favorite flavor is, and keep it for emergency use only. It won't spoil. A GI ammo can or two keeps ammo really well. You aren't going to be plinking or "training" during WROL times. That's stupid.
Don't neglect a couple bricks of .22LR, either. Being able to pot a rabbit or something might be very handy until the grocery stores get back working, or you can get to them.....
) and let's hope that you never have to use it, OK?