Buffy the Vampire Slayer is my all-time favorite TV series. Not only do I love Joss Whedon, but I love pretty much everything he has ever made.
I own all 7 seasons on DVD, and have watched all of them probably three-four times, some episodes I have seen more (like the musical episode, it is fun to have sing-a-longs!).
Buffy started out as a movie and did not make much noise, and was not very well-received. Joss Whedon realized that he had not done what he wanted with the movie, due to others involved in the process, and created the television series, in order to tell the story he was not able to tell with the movie.
When Buffy first came to television (in 1997), I was eleven and watched it with my parents and my little sister. It used to scare me, which is funny because when I watch it now it is not scary at all! Especially the first few season, graphics and monster effects have come a LONG way since then (so has style, just watch the first episode...wow. Which is funny because in that very episode Buffy notes that she can pick out vampires because only someone who'd been living underground for ten years would think that shirt was still in style).
I think that this is a great show for all types. It has wonderful humor, great fight scenes, and a strong cast of characters who you grow to love. I personally love the strong female leads, gives young girls the realization that they do not have to be reliant on anyone and can take on the world.
Other things you should check out if you already know and love Buffy: Angel, Dollhouse, and Firefly. They all have Whedon's characteristic humor and style (Whedon has also done a lot of guest directing on television shows, work on films, and made/been involved in the creation of many musical pieces).
What about you? What is your all-time favorite TV show? Is it as good now as it was then?