My brother is 8, almost 9 years old and ever since he was two I have showed him the awesomeness of the SNES and NES. I wanted him to start with something easy and fun, and now he is playing really complex games on the 360 and PS3. The amazing part though is, unlike most kids his age (or even older than him), he still loves old games and will still play my SNES and any older console and never complain.
I think it is how kids grow up that affects what kind of games they are going to play in the future. Like several people have said before, if a kid's first game was Halo or Gears of War, they are going to look back at older games and automatically call them crap because they don't look as good as new games and never give them a chance. With my brother though, I taught him at a young age to respect games no matter how old they are and to give them a chance.
And as a bit of advice, you shouldn't say that everything modern is crap. There is still plenty of great stuff that comes out (Fallout 3, Valkyria Chronicles, Metal Gear Solid 4), and in every generation there is going to be crap. I am sure there were some pretty shitty games and things back in the 80's and 90's too.