Regarding ages I think younghters can enjoy Mario Bros, Tetris and many other classics as much as older people can.
However once you've played better versions, for instance after playing Super Mario World the original Super Mario Bros feels a lot less special. IMO this goes for gamers of all ages, however for those who've grown up with certain games they may have fond memories of, people may experience additional nostalgic feelings replaying their oldtime favourites. The same goes with regard to movies and other things, they may also better suit what people have grown to like. For instance I like many music from the 80s, while I don't really like many of the new songs my kid sister likes to listen to.
Younger kids can vividly enjoy themselves playing on their parent's Amigas, Snes, c64, etc. But often around puberty they want to fit in with more mature people or at least they pick games what they think is mature gaming. For instance, Gears does not have the wow factor for me. For me such a game requires more depth (no "Boom Boom", like those stupid Boomers say or ultra macho shallow comments from the 'heros' making the game a lot less realistic and appealing for me), a well done story line, etc. IMO Gears' design is mostly geared towards adolescents.
Gears IMO is a bit like what A-team was in the past.
