Making a brilliant, original horror film is pretty hard these days, since practically everything has already been told, and more than once. Using that premise, director Wes Craven and screenwriter Kevin Williamson came up with Scream, whose cleverness derives from the fact that it knows every single stereotype of the genre and satirizes them.
Take the opening sequence, for example: a young girl (Drew Barrymore) is making popcorn and waiting for her boyfriend when she suddenly receives a phone call. Normally, this would be a huge clichè, only this time the killer decides to play a little game (horror film quiz, naturally) with his victim. In fact, the only reason why he kills her is that she gave the wrong answer to one of his questions (those who haven't seen Friday 13th might want to skip that bit, as it spoils said movie's ending). That scene is both very scary (the murder is quite graphic and disturbing) and at the same time funny (it tests the characters', and the audience's, knowledge of the horror genre), and the rest of the film continues in the same vein: after the first killing, the masked psychopath starts disposing of other teenagers in the town of Woodsboro using the same technique. One of the targets is Sidney Prescott (Neve Campbell), whose mother was raped and killed the year before. This implies the killer might be the same, but who could it be? Sidney's distant father? Her mother's lover (Liev Schreiber)? Or some random guy, with no motive at all?
Fortunately, it is not the last category: this murderer has a motive and a plausible identity as well. But it isn't the payoff that makes Scream interesting; it's how Craven and Williamson get to it, by outlining the genre's conventions (some of which were actually invented by the director himself) and using them in a clever, if self-referential, way. The point of the movie is, the more you know of this kind of films (pay attention to the rules, stated by geeky film buff Randy), the more chances you have to survive (although you must take into account that the killer has seen the same movies). The in-jokes that would ruin other films are the very cause of Scream's success, with memorable scenes such as the villain mimicking the movie his victims are watching or Craven's unmissable cameo as a janitor wearing Freddy Krueger's outfit (not to mention priceless lines like "Movies don't create psychos, movies make psychos more creative!").
In other words, Scream is a smart, effective horror film, which manages to amuse and scare in equal measures. Definitely worth watching, even if the two sequels (especially Scream 3) don't really match the original's intelligence and, forgive the expression, originality.