When a film that's had such a bad press as "Buffy" still manages to disappoint you, that's one bad film. For much of its running time it manages to be no worse than mediocre - a sort of sub-"Clueless" (which, to be fair, it predates by three years), with Kristy Swanson doing well enough as a sub-Alicia Silverstone. It also has much the same agenda as "Clueless" of taking a gentle poke at affluent society's rigid class system and wafer-thin "caring about the environment" values. Presumably Joss Whedon's script originally had rather more in this direction; it seems to be set up that Buffy and her class are vampires too, but nothing is done with this idea.
"Clueless" had the advantage of a plot by Jane Austen. As soon as "Buffy"'s plot starts, things rapidly collapse. Disaster is staved off for a while by Swanson's energy, Donald Sutherland's ability to keep a straight face, and Paul Reuben's touching conviction that he's in a funny film. But never has Rutger Hauer's natural screen presence been so totally neutralized by poor direction, unfocused character design and a story that's not only increasingly incomprehensible but not even worth trying to follow. Again, there is an idea here: Whedon seems to want to posit a sort of eternal attraction between vampires and those who slay them, so that being the slayer according to the traditional rules simply confirms and strengthens the vampires' power. But it all goes for nothing.
The fact that the themes and characters are so far removed from that of the spin-off series means that the movie doesn't actually suffer from comparisons with it. It just suffers from being rubbish. Kudos to Fox for being talked into taking on this botched project for a remarkable series, and, for that matter, for suggesting Sarah Michelle Gellar should play Buffy rather than Cordelia. Execs get a bad press, let's give them a moment's appreciation.