I understand why you're asking this. When I rank films it's hard to decide whether to rank them on how much you enjoy them or to try look at them critically/objectively and rank them on how good they 'actually' are. I adore many horror comedies, slashers and low budget gore flicks. These sort of films don't often rank on 'best ever' lists.
I lean towards ranking them based on personal preference. Why list a film high up because everyone else says it's great when you don't care for it ? Also vice-versa, why rank a film you adore low down just because others consider it a bad/cheap movie ?
Most best ever lists are hugely flawed in that;
One thing I've noticed is most of these lists have Friday the 13th (1980) on it, somewhere around 35th-80th. The thing is many F13 fans and slasher/horror fans in general prefer a number of the sequels (it seems you're the same, with part 2 being your favorite). I'd have parts 4, 2, 6 and maybe even 3 over the original.
So yeah, I say rank 'em how you like 'em. It's more interesting that way and your opinion is as valid as any other. For the record, when it comes to slasher films belonging on greatest of all time lists. My top 5 horror films are Halloween (1978), The Texas Chainsaw Massacre (1974), Black Christmas (1974), A Nightmare on Elm Street (1984) & Friday the 13th: The Final Chapter (1984). All slashers.
So yeah, slash away my man.