This is a tough one. 1989 was the year I got into hard rock music. There are so many on this list that I could never part with. Before anyone says what about this band and what about that album, I can only list 20 and I only listed the albums that to me anyway got the most attention in America. Unfortunately I had to leave off Little Ceasar, Bonham, Banshee, and many others.
For me this comes down to Vain, Skid Row, Badlands, and XYZ.
My choice has to be Vain- No Respect
with Skid Row a very very very close second