In 1984 while serving in Germany I got to see the Monsters OF Rock Tour. AC/DC, Ozzy Osbourne, Van Halen, Gary Moore, Dio, Accept, and Mötley Crüe.
I've seen ALL those bands except Accept(Lol), Gary Moore and AC/DC. I saw Dio with Sabbath(1st concert), and I saw him during his solo career at the Sacred Heart tour. I saw Ozzy with Jake E Lee during the Bark @ the Moon tour, with Motley Crue as the opening act, supporting Shout at the Devil, right before they hit it big.
I saw Alice in Chains open for Van Halen in 1991, and Def Leppard open for Billy Squier in early 1983. That was just before they hit it big, and the Spectrum crowd loved their show so much, that when Billy Squire took the stage, he was roundly booed.
I saw Pink Floyd in 87 at the ancient, crumbling but enormous JFK stadium, where Live Aid took place. It was general admission, and there were over 120,000 attendees that night.
I saw the Dead on the last night of their spring 1993 tour, at Nassau county colosseum. Scalpers were selling fake tickets, while real tickets were going for over $100. However, some stranger 'gifted' my friends a ticket, and I got in just before it began.
I saw Crosby, Stills & Nash in like 1990 at the Mann music center, I saw Boston in 1986, for their first tour since the 70s.
But the real jewel hidden among this list, are the 3 times I inadvertently saw Dokken in concert(coincidentally, they opened for 3 bands I had bought tickets to see in the 80s)! Lol