The first two tapes Marc got when he was 10 were "Thriller" and a collection of hits from 1983. Just under a decade earlier, I, too, started my life as a music listener by listening to Top 40 radio and the weekly countdowns of the hits. But the big hit LP then was "Rumours" (even if the first LPs I bought were by Elton John and Queen, and the first one I was given was the Beatles blue album of late-period singles).
I'm not a great fan of "Thriller," and I haven't listened to "Rumours" in ages, but what I wonder is this: how much was my taste influenced by the dominance of Fleetwood Mac in the mid-70s, and how much was Marc's influenced by the similar dominance of Michael Jackson in the early 80s?
More generally, if a band or artist dominates the charts when you first start listening to lots of music, how much does that determine the main directions of your taste? Even if you dislike the band or artist in question! (I can see in my own son's listening habits that many kids discover music through the top 40; it's a way to share things with your peers.)
To be more personal again: Fleetwood Mac ain't actually that much different than The Grateful Dead (the latter just jammed more and didn't have a great female singer), so my taste for the Dead might in part derive from all the Fleetwood Mac I heard on mid-70s pop radio.
True, by the time I got into the Dead, I had turned away from pop radio (and thus, as it was the early 80s, from Michael Jackson), but it would be the pop of my first years of listening that would have had this influence, not the pop of my first years of college.
Or maybe I just became a Deadhead because they played at Stanford a couple weeks after my freshman year began. :-)