I've seen so many great concerts over the years. Heart when Ann and Nancy were young and thin, Boston on tour for their first album, Beach Boys when they were all still alive. Johnny Cash with June Carter and the Carter Family along with Carl Perkins and the Tennessee Three and the Statler Brothers.
Elton John, Mamas and Poppas, The Kingston Trio. But I guess if I had to pick one it would be:
Eagles - Hell Freezes Over Tour
No opening act. The stage was dark, strobes were firing in cloth hanging above the stage making it look like lightening in clouds followed by thunder over the PA system. This goes on for about 10 minutes and then, with the stage still dark, the intro to Hotel California begins and goes for about 5 minutes until it reaches the 3 drum beats that transition from the intro into the song. On the third drum beat, the stage lights came up and the band went directly into Hotel California. 20,000 people went nuts and the concert just got better from there!