If something gave audiences thrills and chills once, why wouldn't it scare the beejesus out of them again? Moviegoers know this isn't always true; so do film producers and executives, though that's never stopped them from pumping out more stories of slasher-flick icons, old-school monsters, reanimated corpses, surveillance-cam–captured ghosts, city-wrecking Kaiju and chest-bursting aliens to keep their bank accounts full. Usually, this endless milking of franchise cash cows means extreme measures (let's do it in 3-D! Or have the killer go to space!) and diminishing returns, and fans move on to the next thing.
Occasionally, however, a horror-movie series can produce a sequel, threequel, or prequel that mines excited new territory, pushes its mythology to bold new places and, on rare occasions, be equal or superior to the original. Just because Freddy, Jason, Godzilla, or your run-of-the-mill xenomorph has a movie or two under their respective belts also doesn't mean that there aren't more horny teens to stab, razor-sharp puns to be delivered and genuine oh-my-god shocks to be had.
So after countless, bleary-eyed hours perusing old (and hopefully not will-kill-you-seven-days-after-you-watch) videotapes and DVDs, we've picked the top 20 horror-movie sequels of all time. These were the Part II's and beyond that kept the fun and the scares going.