A few of the best:
Rolling Stones 1989 Alpine Valley, Wisconsin, outdoors, best sound/acoustics of any Stones show I've seen.
Tom Petty, mid 90's, Fiddlers Green, Colorado, outdoors
B52's, mid 90's, Red Rocks, Morrison, Colorado, outdoors
U2 at the Then World Music Theatre in Tinley Park, September 1992 during the ZOO TV tour was pretty hard to top, that should had everything. Best U2 show i ever saw, and i have seen them at least 6 times
One of the worst concerts I saw was Three Dog Night. They were minus a dog that night because drug abuser Chuck Negron had gotten into a car accident (wink wink). Their harmonies were way off without him. But a great band opened for them that blew 3 Dog Night off the stage that night. They were called The Phlorescent Leech. I didn't know who in the hell this band was or did I care until they started playing familiar songs like It Ain't Me Babe, You Baby and Happy Together. The Phlorescent Leech turned out to be aka Flo & Eddie aka The Turtles. These guys were a great hard rockin' band when they played live.