I've attended roughly a thousand concerts and have seen at least 500 different acts. Being a huge Springsteen fan, I've seen Bruce and the E Street Band about 125x. Other acts I've seen dozens of times include Southside Johnny & the Asbury Jukes (~80), Billy Joel (~60), Elton John (~40), U2 (~30), Tom Petty & the Heartbreakers (~25), and Mary Chapin Carpenter (~25). Acts I've seen at least 10x include Rolling Stones, The Who, John Mellencamp, Chicago, Doobie Brothers, Jackson Browne, Steely Dan, John Fogerty, Huey Lewis & the News, Don Henley, Rod Stewart, Lynyrd Skynyrd, CSN, Garth Brooks.
I'm not sure where to start when it comes to most memorable... just too many.
A couple unforgettable shows that definitely would be on the list: The 25th Anniversary Rock and Roll Hall of Fame Concerts at MSG in 2009. I went both nights. Unbelievable. Take a look at the acts. Simply.... WOW!
https://en.wikipedia.org/wiki/25th_Anniversary_Rock_and_Roll_Hall_of_Fame_Concerts#:~:text=The 25th Anniversary Rock and,$75USD and $2,000USD.