Wow...Tough one...Not necessarily my favorites, but certainly some that have made a huge impact on the music industry...
Eagles-Hotel California (maybe the most famous rock song ever written on this album)
Pink Floyd-The Wall (spent, what?, a decade in the top 100 best selling. Might still be there for all I know)
GnR-Appetite for Destruction (started the end of the typical '80's "hair bands", thank god

)
Metallica-Ride the Lightning/Master of Puppets (whole new genre of music comes to prominence)
Nirvana-Nevermind (same as above)
Garth Brooks-Thunder Rolls (I'm not a country fan, but this album was everywhere. First country cross-over mega-hit in 10-15 or so years. The last I heard, country is still the top selling genre of music, and IMO this album is why)
Santana-Supernatural ("Smooth" was one of the most successful songs of all time and one of my favorites for sure)