License to Ill and Appetite for Destruction were the two that I most remember hitting like a ton of bricks. Both were like, "Oh wow."
I guess Illmatic was like that, too, but somehow I knew about Nas before it came out. Maybe from that song he did with MC Serch. But I'd never really heard the Beastie Boys or GNR until they burst on the scene, so it was more eye opening. To me, anyway.

Thank you for identifying yourself as a goober

Straight Outta Compton - NWA

Also agree with RATM and Weezer which has been mentioned.

Grew up in the grunge/alt rock era so I'm biased, I regret nothing

DMX It's Dark and Hell is Hot

not one of the best of all time, but the title is awesome, Ludacris' debut Back for the First Time

Oh shit I forgot Facelift-Alice in Chains

Rolling Stone lists "License to Ill" as it's #1 debut album.

Also.....

'Enter the Wu-Tang (36 Chambers)' - Wu Tang Clan
'College Dropout' - Kanye Douche

While a fun album at the time, it does not have longevity.

I concur, was big into them as a youngster, I'll probably catch some flack for this but I really liked Korn's debut album, not sure how successful it was though

The guitar center all stars.

the Creed of their day

I disagree, the Clash put out a lot of great albums, but to me the S/T debut is perfect.

Someone probably already said Dark side of the moon.