Freddy VS. Jason = Epic Fail, though I will say I loved the scene of Jason with a flaming machete if only because, well, it was a flaming machete. And, in very brief defense of Friday the 13th, any movie in which the killer dispatches his victim by slamming them against a tree while they're hiding in their sleeping bag is at least alright by me.
The 'Nightmare' movies still get under my skin sometimes - especially part 3, with the guy strung up by his veins / tendons / whatever and marionette-d off the roof and part 5 for the scene with the motorcycle.