It's not about sales though.
Because if it were, we'd be talking Hammer, Whitney, Celine Dion, Garth Brooks and Metallica and sh*t like that.
She said two albums, not artists. The Chronic changed Hip Hop, more than any other project for the first 1/2 of the decade. And anybody that was around back then, knows that Nevermind did the exact same for grunge/rock. It's not about sales or who we think was better. It's about impact. Which is why Buzz from The Melvins said, "We taught Nirvana everything, and they took what we gave them and became the face of the era." That's just a fact.