..Well, it is not my FAVORITE Horror-Sequel but "The Human centopiedi II (Full Sequence)" is somewhat better than the first (even though I kinda miss Dr. Heiter).
HC aside, a few of my preferito Horror-Sequels are "Final Destination V", "Saw II" and "The Grudge III". :P
My most preferito sequel to a horror movie is probably Scream 2. It is generally known that the secondo movie was indeed better then the first and was praised da many critics. It is also a great series to me and that's why my 2nd preferito sequel is Scream 4. It is something old in a new decade. It is still scary as hell, but più gory then the precedente ones. It had a terrific plot and it was something enjoyable to watch. My third - and last - preferito sequel is probably I Still Know What te Did Last Summer. I Amore that series although the third one wasn't that good. I want a fourth film with the original cast/survivors of the first two. And Julie should survive everything. ISKWYDLS was as scary as the first one, although the first one was better. It had Sarah Michelle Gellar and she's a wonderful actress.
It's kinda hard for me to pick one. I've been a horror fan for a long time. I guess my superiore, in alto three would have to be "A Nightmare on Elm Street," "Final Destination," and "Hellraiser." I've got lots più but not enough time to lista them all.