I think a big part of it is simply that people who are 17 and younger are growing up with the Xbox and PS2 as their starting base, where others like myself were starting with the Atari XEGS, 2600, NES, Master System and such. We've seen where the technology was years ago, and where it went as the years rolled on. We have the perspective and sense of history from being there that 17 year olds today don't thanks to actually having been there, and we played the games with graphics that had four colors... and were wowed by them. So we know how things were from a view point that simply can't be recreated when you're 17 and playing games that are older than you.
See, when you're there to play Pitfall! on the 2600 the week it was released, it gives you a perspective that can't be reproduced, even by a child playing that game as their first one in 2010. When that game was new, it was still cutting edge stuff, not retro. So unless you've sheltered that 2010 child, even they will know it's old and that the newer games "look prettier." As a result of all this, when you're in your 30s, you can still appreciate the games from your youth in a different manner, more than a teenager playing those games some 25-plus years after their original debut.
Of course, when you factor in all the short attention spans that have been more the norm these days, is it really all that shocking that 17 year olds don't stick with their games very long? I can still play my 1987 Atari XEGS version of
and have fun with it. Meanwhile, the 17 year old who beat the single player side of Halo Reach, will likely never touch that aspect of the game again. Which brings me to another topic... multiplayer.How many remember when games were single player only (or if it had a two-player mode, you took turns playing)? Now, it's more like, "Single player? I wanna go online and play with my buddies, not play alone." The single player mode of a game is getting a lot less attention than it used to, as multiplayer is where everyone's focusing... to the point that if a game comes out that's single-player only with no online play, it gets bashed left and right for not including it (Torchlight anyone?). It's as if somewhere along the way, people forgot about just zoning out with a game, and how it could be just you against whatever the programmers felt like throwing at you.
Anyway, enough "old man yells at cloud" rambling. The gist of all this is that if you're a 17 year old playing a game for the first time some 20-plus years after it was released, you're not going to have the same perspective as someone who was there when the tech and game was new and cutting edge. And 20 years from now, the same will be true for those who grew up with the 360 and PS3 as their starting point, when addressing those playing the XBox 1080 and PS6.