I think it's a question that's obviously addressed to the fans (who are more likely to have seen all the movies?) so what do you make of the other users lol?
Besides, I have the feeling that this is like for every slasher franchise, the first one or two are always considered the best... so it's not like asking which "Rocky" or "James Bond" is the best...
Not saying Chucky doesn't deserve a poll but I don't think the series isn't big and good enough to make us truly wonder which film is the best.
Jeorj Euler