First concert was Triumph's Thunder Seven tour, they opened for Aerosmith. No idea how Aerosmith was that night. I vaguely remember one of the other boys mothers smoking a hand rolled cigarette. My how naive I was.
Best concert: Hmmm, the easy answer would be Pearl Jam, just not sure which show. In reality it was probably when my wife took me to my first Tool concert. I recall walking out of it with my eyes wide yelling "Now that's what Rock and Roll looks like in the 21st century". I was in awe. I then promptly realized I had no idea where I parked the car. Strangely that wasn't the only time I lost a vehicle at a concert.
Other notables that round out the Top 5:
Depeche Mode Songs of Faith and Devotion tour
My first Symphony experience. Watching the orchestra work its magic and reveling in the acoustics of the room while all dressed up and fancy was fantastic.
Dual headliners of Metallica and G&R with Ice T's rock band Body Count.