I guess most of the great concert experiences I think of involve classical music or jazz in really small venues.
I am reminded of an internship in college and rooming next to a guy a little older from NJ. I started telling him about great concerts I'd seen. I told him about Jefferson Starship and he told me about them being Jefferson Airplane. Me: Robby Krueger him: the doors.
Me: Neil Young him: Buffalo Springfield. I guess the best of those rock concerts was Devo - they were pretty incredible.
So now many years later I'd have to say some of the concerts that made the biggest impression were:
the Tokyo String Quartet at the UofI. They played the Ravel string quartet. I'd never heard that before and was just blown away.
the CSO with George Solti playing Beethoven's 9th. It was opening night of the season so the choir sang the Star Spangled Banner. I didn't know it could sound that good. And then the 9th was transcendent.
the CSO with Michael Tilson Thomas doing Mahler's 6th. Incredible and disturbing at the same time.
Keith Jarrett a couple of years ago. It was great. I think a lot of it was just being so happy to have seen him live.
Not a concert, but seeing the Magic Flute in the old opera house in Paris was pretty spectacular. Natalie Dessay nailed the queen of the night arias which she did not perform live many times.