Nightmare on Elm Street - I enjoy most of the series and like how they try and differ the films. 4 and 5 might not be popular but I actually really like them and think five is hugely under-rated.
Friday the 13th - Problem with the series is that it is too repetitive and the same thing happens in every film of the series. They tried to go different in some; 7 has that girl with telepathic powers and 10 was set in space but still not amazing. Part 2 and Jason Goes to Hell are the best in the series in my view.
Halloween - Better than Friday the 13th, but like Friday the films are again repetitive. 3 had nothing to do with the series, and dont get me started with the one with tara banks. Plus Rob Zombies remakes were terrible, but I did like the Part 4 and 5 with Danielle Harris
Elm Street > Halloween > Friday the 13th