You went into this movie with the completely wrong expectations than. If you were expecting an expertly crafted story with lots of character development for our protagonists to get us emotionally invested in the story, you went to the wrong movie bud. Every single Friday the 13th film (including the original) was made for one purpose and one purpose only: gore, nudity, and drug use. Those are the three calling cards of the slasher genre, and trust me, that's all these films have ever tried to be. They aren't looking for any Oscars.
Umm...no, the slasher genre IS a genre of film. That's not up for debate, the slasher genre has certain distinct aspects that make it fit into the category.
http://en.wikipedia.org/wiki/Slasher_film
It's a subgenre of horror, and I'm sorry man, but that is not up for debate. Haven't you ever heard of subgenres before? The Beatles and Metallica are both "rock" bands but obviously they play different
styles of rock, right? Same concept here.
If you want good horror films look to Europe, because American horror is in the toilet and has been for a decade. The best horror films in the world are being made in France right now, if you want a great horror film I'd suggest Inside or Martyrs.