Buffy the Vampire Slayer is not only my favorite show, but is so with an impressive margin. I am stating it that way to emphasize how great Buffy is, not to denigrate other great shows, of which there are plenty.
One reason Buffy is head and shoulders above others is the many dimensions in which it offers entertainment: drama, humor, suspense, action. It has elements from several themes, including horror and science-fiction. Because of this broad coverage, I have heard many times people struggling with placing Buffy in a genre. I do not find that hard at all: I think Buffy is clearly Fantasy. It contains all the hallmarks of Fantasy, though its setting is contemporary.
Buffy's greatest strength is that despite some of the show's corny fantasy aspects, the drama is incredibly real. Buffy has a family, she has friends and she has lovers, and they are all life-like, fallible people. They lie to each other and let each other down and support each other and lift each other up in ways that are more literary than soap or genre. I find it supremely ironic, but one of the most supernatural shows that have aired on TV contains some of the most plausible character-driven drama.
I recently watched the fourth season (for who knows which time), and the first episode, The Freshman, is a good case in point. In it, Buffy struggles to adjust to campus life. The episode serves as a good miniature of the show as a whole. While Buffy has to deal with real-life struggles, she is also, for the first time since facing the Master in the first season, bested by vampires. The metaphoric parallels between her real-life struggles and her combats against demonic villains are sometimes pretty thin, but they still work.
I believe all great shows must have great writers. Buffy gave me a reverse observation of this. After I had seen it once or twice, the episode "Inca Mummy Girl" became almost boring for me. I checked the writer to see which other shows he had done and whether I found the same lack of quality. It turned out the writer had only done that one Buffy episode. It is not badly written, but it lacks the quirky humor and the edginess of the rest of the show.
I think the best season is the third one, and I may write about that later if the fancy strikes me. Like most shows, it is best if watched from the very beginning, though.
Purpose one: writing a travelogue to describe my various trips.
Purpose two: muse.