The Beatles White Album, sure (though really it was probably Revolver). Ziggy Stardust, of course. Never Mind The Bullocks, no doubt. Joy Division's Unknown Pleasures, perhaps. My Bloody Valentine's Loveless, of course -of course! (though I still think Isn't Anything is better.) An argument could be made for Slanted & Enchanted.

What's the last record to radically change the landscape of music? Or if not the last one, then one I've missed in my 30 second thought process recaping pop music history.

Me:
Source Tags & Codes. This record will be loved 30 years from now. Relative Ways has one of the simplest, yet most disarming, striking choruses of all-time: It's OK. I'm a saint. I forgave your mistakes.

And those records which are thought of as revolutionary but aren't?

Me again:
Nevermind. Ok, it's good. But revolutionary? C'mon now. Grunge refers to the same rock 'n roll music we always have loved - those Seattle bands had unwashed hair and Pendleton shirts is all. For those that disagree I got one word for ya: Dinosaur!