Metallica and Queensryche in 1989.
It was Metallica's first headling, arena tour of the States, and they were supporting "Justice", at the time. I was knocked out...it was unbelievably good.
Queensryche opened, supporting "Mindcrime" and, again, just blew me away.
Another great show was King Diamond and Sepultura on Halloween 1989 at New York's old "Ritz" theater. At the time, King was probabaly my favorite artist....he was supporting "Conspiracy". The stage set featured the old house, 'grandma', and King being burned alive in his coffin (during Cremation) only to disappear when the coffin was then opened! It was simply unreal. King's vocals were also much stronger live than i expected them to be.
Sepultura opened, supporting the recently released "Beneath the Remains". I remember then thinking that these guys would be huge, but I guess that never really materialized.
Finally, my third fav gig was also in 1989. Tesla with Badlands (Jake E Lee's old band) opening. I went really only for Badlands who have released one of the top ten all time great albums in their 1989 debut!
They were, of course, blazing! Gillen's vocals (RIP) were immense....he's really right there with Ian Gillan, Robert Plant, Glenn Hughes, Halford, Dio, etc. A true vocal god.
And after seeing Tesla that night, I became a fan. No frills, no cheese....just kickin ass!