I agree that when you really need to defend yourself, sights will be the last thing you will be thinking about. As for long guns, if you can hit with a shotgun then you are good enough in my thinking, your rifle will point just as well as any shotgun.
Learning to hit instinctively with a handgun may take a little work. I would start by picking a gun that points the best for you. My first handgun was a S&W. I used to shoot at running cottontails with it a lot and never hit one. Then I bought a single action 22. All of a sudden I could hit running cottontails, not every time by a long shot, but enough to tell me one gun pointed where I looked the other didn't.
I was in an almost real life situation once that showed me how things might really happen. It was a training scenerio at a cop school I was attending. We were given paintball guns for the exercise. My partner and I went into a room and right away things started going bad. One bad guy was going to "show" me his new shotgun. I grabbed the barrel left handed and forced it up. We thrashed around long enough for me to decide this was more than a guy wanting to show me his new gun so I started to draw mine. When I started to draw, the bad guys partner went for a handgun in the couch. Almost without thinking and while still wrestling with the first guy, I plugged the guy with the handgun three solid hits. All this happened so fast that my partner was still standing there picking his nose when it was all over.
This was across the room distances, so accuracy, even for point shooting, was not a big issue. But then you watch some of these survailance camera shootings that are all the rage on the tube these days, and you wonder how anyone could be such baaad shots as some of these people. Especially the crooks seem to be laughable. The storekeepers are usually some better.
Common guys, this is something that we really do need to be better at, I don't want to see one of our own on a camera some day blowing away 6 or 9 shots and not touching a feather.