When they started friday 13th had shockingly cheap production values, like it had been filmed through a doorway insect net! Halloween n Nightmare were always better produced and classier. First 3 Freddie films and then the first 2 halloween films - the rest was repetitive crud that lost its edge and originality.
I loved Halloween, and sort of liked Halloween II (the ones from 1978 and 1981, not the horrible Rob Zombie remakes). Halloween III: Season of the Witch was an interesting failure. The rest just plain sucked.
I didn't really care for the Friday the 13th series. It was just too silly overall. Although, a few of the films had some good-looking girls in them, particularly Friday the 13th - Part V: The Final Chapter.
A Nightmare on Elm Street was excellent. The second one was extremely bad-to-mediocre, but A Nightmare on Elm Street 3: The Dream Warriors somewhat redeemed the franchise ever-so-slightly. Unfortunately, the rest just plain sucked...
I like the Nightmare On Elm Street series the most because Freddy, unlike Michael and Jason, has a personality and a (admittedly sick) sense of humor. Michael and Jason are just weapon-wielding hulks who may as well be robots/terminators.