Inferno & Deader are the hidden gems hidden under the fun junk.
Hellraiser 1 & 2 are complete masterpieces of Horror cinema in their own right,3 is schlocky fun,4 has it's moments but as overall film it's lacking & than after that the franchise went DTV with two only amazing films that came out of that pile.
The first DTV sequel Inferno is quite possibly the best film in the whole franchise with it's cool crime noir story that's has a Pinhead spice.Hellseeker the 2nd of DTV sequel is a very enjoyable film but it's a lesser version of Inferno, & than we get to the last good entry in the franchise Deader of which played with Hellraiser mythos very interestingly with it's cool cult story and locations.Then the last two Hellraisers we're awful.
So to me it's Hellraiser & Hellhound:Hellraiser II are great horror tales then you can skip the fun but ultimately lacking III:Hell on Earth & Bloodline and just get into Inferno of which is a really cool film than ignore Hellseeker and jump into Deader.
Hellworld and Revelations are just disasters that insult the franchise.
Hellraiser,Hellhound:Hellraiser II,Hellraiser Inferno & Hellraiser Deader are the four worth watching.