Yeah, I think Kael pretty much trumped any response in this thread ever. Perspective, guys.
That said, for me it's not so much the defilement of childhood entertainment (I've grown numb to that), but the physical transformation of the landscape.
Growing up, I lived out in dairy farming country, where there were numerous farms just down the "highway" (which was a two-lane state road). We had no streetlights, and there was basically one main road in either direction that went "into town", said town being several miles away. You rode through thick forest with few landmarks. Every house you passed (and there weren't many) was set back from the road a good 500 feet or more, usually on a plot of land 3 or 4 acres (or more) and often with its own pond.
The nearest store was an honest-to-God "country store" about a mile up the road that sold everything from leaded gas to sliced bread to shotgun shells to udder cream (when it was still used for cows and not as a hand lotion) to baskets of penny candy for the kids to drool over. You wanted anything more than that, you had to go into town.
At night, it was pitch black. You could see hundreds of stars, not just the forty or fifty that I can see on an average night now. It was also deathly quiet. You could hear a squirrel step on a leaf halfway across the yard (and our yard was an acre and a half of land).
When we played, there were no borders. We roamed through yards freely, we climbed trees, we fought duels with tree branches in the middle of the street. We roamed through the forest setting up forts and traps, preparing for the inevitable day we would have to fight guerrilla warfare against the Red Army.
Red Dawn came out when I was 8. It was kind of a requirement in the mid-80's that you planned for the Soviet invasion if you were a kid. It was like our zombie apocalypse.
Now, when I visit home...it's painful. I see strip malls where there used to be forest. Corporate office parks where there were farms. There's a big shopping center where the country store used to be...the actual spot where the store was is all parking lot. Where friends' houses used to sit--where I learned to ride a horse, where I learned to shoot a rifle, where I had my first shy kiss--it's all asphalt and manicured shrubbery and tasteful brick storefronts. That little two-lane road is now a busy six-lane highway. The streetlights keep the area permanently lit in a orange sodium glow. Though not obvious, if you listen you can hear traffic noise at all hours of the day or night.
The thing is, it's not like it happened overnight. Which makes it harder to remember the way it used to be before all of the "progress". Some of the development happened when I was in high school. Some of it in college. Some of it after that. So then I'm left going, "Yeah, that used to be ******. Wait, what was it before that?" Sometimes I stare at a patch of buildings, and I really REALLY try to remember. And it just doesn't come. I can remember what it looked like five years ago, ten years ago, maybe 15. But remembering what it was like when I was an actual child just doesn't happen much anymore.
Sorry to sound so maudlin about it. It's just that I'm a very past-oriented person. Probably why I majored in archaeology and history the first time around. To some extent, it's the sadness of an archaeologist seeing the artifacts of his own life being looted and lost.