My mother discovered Three Company’s in syndication and loved it. She had a crush on John Ritter.
Amongst the younger people I know, they seem to like modern rap/R&B/whatever until they are about 25. Then they become huge classic rock fans, wanting to know everything about 1960’s music. Tell a 20 year old rap won’t last as long as rock and they won’t believe you. A 30 year old will agree.
Bwuh? This doesn’t make any sense.
Rap has already lasted longer than the period in which “classic rock” was created.
I get that people can have individual pop culture interests that have their roots before one’s time (I have some myself), but I know what the OP is talking about … it’s not that Marshall as an individual can’t have an Evel Knievel obsession, but it feels a tad off for him to make that reference as a general culture thing as opposed to a personal interest thing. (And God knows if it was a personal interest thing, HIMYM would have done an episode on it.)
I notice this a lot on Psych, Sean and Gus are supposed to be around 10 years younger than I am, but I’m pretty sure the writers are exactly as old as I am. (I just looked up two of the writers who have done multiple episodes at random, and yeah, they are my age.)
He’s too young now, yes, but that episode aired in the mid-to-late 90’s when Pogs were in their heyday. As for ALF, well…yeah, he would have been a little too young to remember it originally airing…but he would have been the perfect age when The Simpsons first aired ~seven years earlier, so I’ll give the writer’s some freedom to “play” wit the relative ages.
They even made fun of that themselves in an episode where Homer describes his childhood and said it was the 6’s, or the 7’s, or it might have even been the 50’s, he couldn’t remember.
And the most recent retcon (in the 2007-2008 season) had Homer as a young man who started a grunge band in the 1990s. 
“I’ll study tomorrow and tomorrow and tomorrow.”
“You sound like Z-man!”
“And Z-man sounds like Will Shakespeare…”