The premise of the movie is as follows: in 1986, a ten-year-old named Justin Schumacher suffered a concussion at one of his break dance competitions that left him in a coma for twenty years. That's where the comedy, 'Kickin' it Old Skool,' comes in. Now, apparently, it is the '80's that are making a comeback, as those who were kids in that decade begin to edge their way ever so reluctantly into middle age. In the 1970's, audiences escaped back to the more innocent and halcyon days of the 1950's through works such as 'American Graffiti' and 'Happy Days,' while in the '80's, it was the '60's that got replayed, via 'The Wonder Years' and 'The Right Stuff.' In a similar way, 'That '70's Show' came to define nostalgia for the young adults of the '90's.
That's just about the point at which the youngsters of a particular era will have experienced enough of adult life to start them pining away for the 'good old days' of their pleasantly carefree and invariably misspent youth. The way I figure it, it takes about a good twenty years for a decent nostalgia trend to kick in.