Wow, you guys are my people. I've always really liked Firefly, and I think it's far and away the best first season Joss has ever produced, but it is overrated to the max. Buffy and Angel may have had way more duds, but their longer lifespans allowed me to get way more attached the the characters and invested in their world. This isn't really Firefly's fault, as it was canceled, and I'm sure it could have been Joss's greatest work if it had been allowed to go on as long as he wanted. But we got what we got, a really good show with lots of unrealized potential, but not much more.
Plus, I have somewhat of an irrational resentment towards it. If Joss hadn't been working on it, he could have paid attention to Buffy and Angel and their quality wouldn't have dropped. Also: Farscape and BSG > Firefly.