Sadly, I never got to see Led Zeppelin.

1. Van Halen at Mobile Auditorium. Back in their early days with David Lee Roth.
2. Rush R40 in N.O. Saw them many many times before that but the R40 final tour was by far the best.

There were many other big name concerts (AC/DC, Aerosmith, Def Leppard, Kiss, etc) but they are not in the same class as those two.