The first movies in the Nightmare on Elm Street
franchises are pretty great.
The sequels of all three series are, well, programmers, with the exception of Wes Craven's New Nightmare
, which is one of the most inventive horror sequel ever made. so, based on that merit (and the fact that the Jason movies are all crap to one degree or another, albeit often enjoyable crap) I'd give the edge to Freddy.