My first three concerts......
Alice Cooper BDB tour in '73 - Still one of the best shows I ever attended, with the original band members this was a concert for which to judge all that followed.
Led Zep Houses of the Holy tour - Still the worst show I ever attended (that includes the Ratt show I walked out of!), a total drunken snorefest that included a 35 minute drum solo as part of Moby Dick. Great band in the studio, live, no.
Jethro Tull Passion Play tour - While not a show in the Alice Cooper since, JT (with Hammond -Hammond on bass) was really good, there were spot on, not sloppy and played the entire album without a break, after which Anderson said "And now for our second song"