Hellraiser 1 and 2 are amazing.
Then skip the rest and watch Hellraiser: Inferno and Hellraiser: Hellseeker. Those two are more standalone stories, and more akin to Silent Hill than the first movies.
I only watched bits and pieces of 5, I was constantly falling asleep (I don't want to blame the movie, I was really sleepy, but yeah ... it also wasn't that engaging).
Hellraiser "in space" (4 I think) is certainly not as good as the first two, and the premise might make it look like the abortion that Jason "in Space" was, but I found it enjoyable.
I'm going to check 5 and 6 anyway, seems I'm missing something interesting.