Well, the first music I was exposed to as a child was "adult contemporary", which at the time meant Michael Bolton, Amy Grant, Whitney Houston, and other pap.
The first time I really remember thinking to myself "Holy crap, music can be AWESOME" was in grade 6 or 7, when a friend of mine loaned a copy of AC/DC's Razor's Edge to me. I loved it, and started listening to them, Aerosmith and a bunch of other hard rock bands from the '70s and '80s.
Then, when I wanted something with a little more "Umph", I went to the pawn shop and bought a copy of Pantera's Far Beyond Driven. I'd never heard anything like it, because in the town I grew up in, there were no real "rock" stations.
That pretty much sums up the first 4 years of my musical life