Neil Diamond at the Tacoma Dome, 1980 I think. It was right after the Jazz Singer movie. Went with my Mom, she was a fan. I wasn't a fan until I saw him live; it hooked me on live music from that point on. He played for over 2 hours, no warm up act.
I've been to dozens since, some as good, others not so much. My favorite was Bumbershoot music festival in Seattle. I saw Ben Harper, Tracy Chapman, George Clinton, and Motorhead all in one weekend there.
The crowds did bother me, but the energy of live music more than compensated for me. Some bands are awesomely better live, others are horribly worse.