If you didn't say if we had to stick to the people you made in the poll or we could name our own favorite killers so I'll do it both ways.
(According to your poll)
Jason Vorhees: I'd say he is the best simply because of the way he kills people, in all the movies he has, he always done something different in one and it was always awesome. One of my favorites was in Friday the 13th: Part II where Jason kills the guy in the wheelchair with the machete to the face and he goes all the way down the stairs or in Friday the 13th Part VII: The New Blood where Jason kills the chick in the sleeping bag by bashing her off the tree! (I know that scene is a bit wrong but whatever, it's a cool kill nonetheless). Countless other awesome kills but those are the two that come to my mind straight away.
(Not according to your poll)
Ghostface: One of my all time favorite killers, Ghostface is just...so smart and the character is so realistic, he doesn't get shot in the head with a shotgun, then get up and keep walking towards the helpless victim. He's believable, the way he phones his victims and gets talking to them and interacts instead of killing them off straight away is very enjoyable too (like the famous opening scene of Scream). He obviously only stays with his knife but it's just the build-up to the kills and everything that happens around them. One of my favorite kills by Ghostface though is in Scream 2 where at the start the dude goes into one of the stalls in the bathroom, to only hear noises from the other stall and puts his ear up to the wall inbetween them. Then Ghostface forces the knife through the wall into him! Man that was such a great kill (not to mention one that happens directly after either, but I really loved that first one).
(One worth noting)
Leslie Vernon: Is he the best killer of all time? No, but is he one funny, very believable, entertaining and smart killer? Heck yes! I loved the movie Behind the Mask: The Rise of Leslie Vernon. Man, it's just the way that Leslie is that makes him so unique and awesome. It's not like he has some of the best kills or anything but he's just so awesome. We see the way through the film that how he works and the stuff he does and dude it's just amazing. I loved the movie and he's a great killer. I was so saddened that the sequel/prequel didn't raise enough money to get one, and yet Paranormal Activity is on it's fourth when BTM is a way better movie? It nearly makes me sick.
Anyway, make what you want of the ones I named