I started watching Buffy back when I was 16. I remember seeing it advertized and thinking 'Oh yeah, like I'm gonna be watching this trash. The movie was totally lame and- heyhey, this sounds pretty cool'.
And from that first time when me and Mom sat down to watch Welcome to the Hellmouth, I was hooked. I mean this show spoke to me. As Lyri said above- the blonde was the heroine and as a natural blonde myself it was just so cool to see her busy not-being-killed and also, more importantly, kicking ass. And the fact she was the same age too meant I could directly relate to what the characters were going through- only without the vampires and stuff. And the more I watched the show the more I felt I had in common with the main character- which had never happened to me before on any show with any character- and I loved that. We the same age, only children with single mothers and in South California...course she had a much better and much more extensive wardrobe than I ever managed. And to be able to relate, especially in your teens, to be able to relate so massively with a TV character was such a big help and I truly believe it contributed to making me who I am today as dramatic as that may sound.
And as Lyri said, if I was ever afraid of the situation I would think of what Buffy or Willow or Cordy or whoever was appropriate for the situation would do and that would give me just that little burst of confidence to help me through.
And what I think makes this show so great IS that relation. I mean whether it's a character, a storyline, a couple, or even just an episode I think each and everyone of us can find something in the show that we connected with, that we feel directly relates to us, almost as if it were written/created just for your benefit.
And I do go through lots of different favorite shows- my current being things such as Supernatural and Private Practice 😉 but despite that and how my favorites and tastes in favorites and viewing habits may vary, Buffy is always there, in the background so-to-speak as a constant favorite. It's the one show that when I'm down about something or I'm missing someone I can flip on an episode and it immediately makes me feel that little bit better. It's been a part of my life for over eleven years and I honestly believe it will continue to be a part of my life and as my life changes, the way I relate to the show and the way it helps me in my life will undoubtedly change too. And I like to think it's a TV legacy I will one day be able to pass onto my children.
It's dramatic, it's over stated, and so many people have said it in the past and even on this thread that I think for the fandom as a whole we're getting pretty tired of it and anyone not in the fandom probably just thinks it's pretty weird, but Buffy is, I have to admit, my hero. Not just the character but the entire TV show. And that's not something that happens often.