In regards to Charmed, Buffy is a year older, and is the kind of show that influenced a lot of the genre that followed it (Sabrina is a sitcom based on an Archie Comics character, so not even worth comparing, they are two different things).
It was linked to the movie thread I believe, but I believe your trouble with Buffy is an effect of the Seinfeld is Unfunny trope. The writing and dialogue are miles above that of comparable shows (Joss Whedon is still really the only person who can do "whedon-esque" dialog well, most who try just get word vomit). The Opening is a good example of what the show's about and tries to do. Spooky old school horror music that becomes remixed into a fast paced rock rift. Whedon takes the old horror and supernatural moves it into the present day, and gives you an action show, with the obvious damsel in distress is now the kickass hero role reversal.
To say it does everything right is being delusional (see my rants about certain seasons earlier in this thread), but Buffy for the most part accomplished everything it originally set out to do, and did so in a way that hadn't really been done before.
