if you've watched the t.v. programme, '100 scariest movie moments,' (or something like that), i think it was meg tilly who said in modern horror movies you're always waiting for that extra 'oomph', that part where mike meyers rising up silently in the background after stabbing him in the eye with a clothes hanger, where jason does the same, where freddy does the same, where, well, you get the picture. it think what she said (if it wasn't tilly, it was a female) is true, too: you always have that little extra bit of action after the hero thinks they've killed the baddie. 'the ring' is a perfect example and even 'alien versus predator' had it. for that matter, 'alien' did it. i'd venture to guess that whole thing started somewhere in the 70's.
is it good or bad? well, it's certainly cliche nowadaze, eh? there's a new 'amityville (sp) horror' movie coming out, and it should be interesting from a movie-making standpoint to point out the differences from 30 year old horror styles and modern scare tactics.
i'm not adverse to killing the protagonist off if it suits the story. i don't think anyone really is, particularly for a movie. they killed the real protag off in 'the exorcist' (though, admittedly, they brought him back for a sequel, but no one questioned his death originally). another (older) trend is to kill the protag off in a sequel once a new set of characters come into the franchise, like 'hellraiser', 'alien' and 'house' and i want to say the 'freddy' franchises. so, maybe that's something to bear in mind, eh? i mean, you might consider keeping the main character around with the intent of eventually killing them off later. as it is, there are just too many movies to list where the protag dies (remember 'the fly' and 'christine'?).
happy endings in general get turned on end. 'poltergeist,' where they all survive, but at a pretty steep material cost, isn't exactly uplifting. this is pretty common in horror, too, eh? like the inherited house collapses in the end.
i'd say there's a different dynamic involved in characterization with a script vs. a book. i can blow off a movie in a couple of hours, but i feel you run a bigger risk having bad things happen in the end of a book, where a person spends a significant amount of time holding in their hands. just my opinion, but i think you've got more creative lee-way with a script's ending than a book's in terms of justification.