How old does a game have to be before it becomes "retro"?To answer that, of course, we need a working definition of the…
Technological progress once swept games into the retro bin within a few years, but no longer – publishers must learn about how to support, not destroy, their older titles | Opinion | GamesIndustry.biz
I think that the demographics of gamers have been skewing older and older, and it's finally reached the point where a critical mass are past the age where they place significant value on the "newness" of a game.
You can still find 13-year-olds decrying PS3 and 360 games as being "unplayable" due to their perceived technological shortcomings, but every year they represent a smaller and smaller slice of the total market. The surveys I've seen lump 18-35 into one group, but I'd be interested to see the results of splitting that into two groups at around 26-27.