among other things it contains a really numb, distressing episode revolving around a character's death, a brutal rape of the main character by possibly the show's most adored male character, an episode that implied the whole show was just the wish fulfillment hallucination of the actually mentally ill buffy, a genuinely surreal dream episode mythologising the characters and their psychology, a silent ep and a musical ep both of which won awards for their ingenuity, etc. it took a lot of risks many of which alienated doting fans, and some of the episodes were stuffed full of subtextual meaning. it was a very thoughtful show, in other words, not to mention frequently hilarious and reviving the spirit of a lot of vintage horror-action-comedy sources. not denying it was a little uneven though.
charmed is pretty shite from what i remember.