After watching Prophecy Girl today I have sort of evaluated the show in my head so...
Buffy
Best Episode - The Gift (beyond brilliant)
Best Scene - *I don't wanna die* Prophecy Girl (SMG gave possibly the best performance of either show)
Best Line - "Willow: It's horrible. That's me as a vampire? I mean, I'm so evil, and skanky — and I think I'm kind of gay." Doppelgangland (It was funny and a good bit of foreshadowing)
Worst Episode - Beer Bad (this episode disgusts me)
Worst Scene - *Demon Old Lady* Doublemeat Palace (just terrible)
Worst Line - "Get Off Me Super *****" Two To Go (so tacky)
Angel
Best Episode - Untouched
Best Scene - *I don't wanna die* That Old Gang Of Mine (I don't know why, but I found Fred's words gut wrenching, more so after the Ilyrria thing)
Best Line - "And yet, somehow, I just can't seem to care." (you gotta love the titular character descending into darkness)
Worst Episode - Shiny Happy People (dunno why, I just hate it)
Worst Scene - *Burrower Demon* Lonely Hearts (just terrible)
Worst Line - "If you don't sign, we'll sue your ass off and kill your children. Just kidding, Donald. Nobody wants a lawsuit." Judgement