I think the fact that Sarah Michelle Gellar never got a single acting nomination for this show is the second biggest snub in the history of the Emmy Awards, second only to Dixie Carter never getting nominated for Designing Women.
Season 5 of Buffy was eligible for 2001, that year were nominated Edie Falco and Lorraine Bracco for The Sopranos, Amy Brenneman for Judging Amy, Marg Helgenberger for CSI, and Sela Ward for Once and Again. I think that SMG deserved not only a nomination, but the win too, or Bracco.
The overall snub towards the SciFi genre is the obvious answer. And yes, both the acting and writing for that episode was an astounding snub.
As well as "Once More With Feeling". How many other shows have EVER achieved the quality of that episode.
All I can hope is that the continued Comic Con surge in popularity starts swaying the Emmy voters to broaden their horizons. It may take another generation or two.
"Buffy" was a pioneer.
Agree with all of you, Buffy was a high quality drama, alas it seemed to be overlooked because of the fantasy aspect, such a shame, those of us who love it will always hold it in high regard though, the only reason I watched 'Ringer' was to see Sarah back on TV :)