Alice in Chains.
Strictly grunge: Soundgarden, Nirvana, Bush (a controversial choice, I know), Stone Temple Pilots, and Local H.
But early 90s alt-rock in a more general sense: Smashing Pumpkins, Tragically Hip, Sonic Youth, Hum, and The Flaming Lips would probably be my top 5.
Honorable mentions to The Pixies, Replacements, Wipers, Sonic Youth (again), and Love & Rockets who were more 80s than 90s, but still pretty fucking awesome.
Don't believe everything that you read.
Soundgarden, hands down. Chris Cornell (RIP) is my favorite singer to come out of that scene.
Temple of the Dog, which was a supergroup formed in tribute to Andrew Wood of Mother Love Bone, also features Cornell with some vocal work by Eddie Vedder, my second favorite grunge singer.
Again, if we expand to 90s alt-rock in general as Just_A_Guy_You_Know did, then Kingston, Ontario greats The Tragically Hip would make my list as well. Though they were already around in the late eighties, just not that well-known yet.
There's an element of heat in this story.
Consuming Fire of Her Desire - Elements comp entry