In my opinion, Pearl Jam, Temple of the Dog, and The Pixies don't qualify as grunge. Certainly Pearl Jam & TOTD got lumped into that category due to their lineage and geography, but as for the SOUND of their actual music, I don't think they count. Pixies are just too unique, and even when they've really rocked hard, it's not actually in a grunge-like fashion.
I think Mudhoney set the standard and truly blazed the trail on a national basis. Of course, they were inspired by some others, but I think they defined grunge. They were also the best grunge band.
Nirvana was a great band, and much of what they did was grunge.
Alice in Chains and Soundgarden are somewhat overrated, and Stone Temple Pilots REALLY overrated.
I can't say I've ever even heard anything by Mad Season....