Not a lot . There are more than a few vinyl "buffs"/ collectors around. You just have to see the number of 2nd hand & vintage record shops around.
All an MP3 really is is a single that you download, so yes. I think my first single was something or other by the Thompson Twins. Embarrassing as it is, my first CD was "Can't Touch This" by MC Hammer - and I bought my first CD player about 1991. My first DVD was Days of Thunder - purchased moments after I ordered my first DVD player.
I still have the Grand Illusion album on vinyl. Ooh, yes, I loved the Hardy Boys, though I was more of a Parker Stevenson gal. I had dozen of Hardy Boys and Nancy Drew books. My First CD was Howard Jones' Human Lib. It's obviously an early CD because the jewel case is much thicker and sturdier than those of today. In fact it's probably the only case I haven't managed to break, and that CD must be over 20 years old.
The musical tastes in this thread are healthy indeed. Me, I don't think I ever bought a single when I was a child. Heck, I never even bought albums until I was 18. I think my first single I ever bought was that remixed version of "A Little Less Conversation" by Elvis Presley. But I had escaped my teenhood for a while by that time. Incidentally the first downloaded single I ever bought was "Crazy" by Gnarls Barkley.
I remember my first single. ABC by the Jackson Five. Bought new while the song was on the charts. I remember my parents questioning my choice-they wanted me to buy an Alvin and the Chipmunks single instead. LOL. side note-I still have the 45 and its still playable. Sucker must be 40 years old.
My first single was "Hound Dog" by Elvis.. My dad bought it for me not long before he died.. As for the first I purchased with my own money? Wow... Might have been "Another One Bites the Dust" by Queen...