Here is a brief opinion of the seires in the order of their release. 
 # - Always great, but stands alone since it's about Pamela and not Jason 
 # - Not bad, but nothing real special 
 # - No true fan can diss the film that sparked a revolution, the attainment of the mask is a quintessential moment of the films 
 # - By far my favorite of the series 
 # - Not my favorite for the very reason that Jason was just a hallucination, and I personally didn't like the up and down emotions of Tommy. Is he going to be the killer, or what? 
 # - My second favorite of the series. There wasn't obligatory nudity, the movie seemed to poke fun at itself but in a serious way 
 # - A good effort. Kane's performance as Jason is a highlight. 
 # - Not crazy about the majority of this film. I like the look of Jason, but I would have preferred more Manhattan time, and the ending was horrible. It didn't make a lick of sense. 
 # - Again, more of Jason himself. Concept wasn't bad, but he's killed in the first 10 minutes, and is resurrected and killed again in the last 10 minutes. People pay to see this guy. Plus there was that whole worm looking thing that was totally stolen from The Hidden. 
 # - I want to kill Jim Isaac for this film. It's shot like a bad made-for-television movie. I hate the look of the "regular" jason in this film. The characters were much more cheesy and annoying than usual, and the puns were horrible ("He's screwed Sarg."???). UberJason is awesome, and I wish there was more of that. Plus, did anyone on that crew see Star Wars? Hello, try and make some minature models for space or something. The CGI in that film are horrendous. Also, when you venture to space, your film is generally sunk already. These types of movies that go to space rarely succeed. Look at Leprechaun. Heck, even when Critters returned to space the movie wasn't as good as the first two.  
 # - The cross-over was a welcomed improvement to the franchise. In my opinion, it's one of the best for both series. I liked how they managed to connect the two characters without actually needing to do any retconning (e.g. original drafts were going to make Freddy a counselor that allowed Jason to drown, or one was going to make him have rapped Jason as young boy...stupid stuff).  

 That's the basic jist of my opinions.