Don't Expect Closure (Spoilers!)
I'm not a hardcore PHANTASM fan, so I don't know how much my opinion matters to those of you who've seen the movies enough times to know them inside and out. (I've seen them all once, save for the original, as seeing the 4K restoration was my second viewing) For what it's worth, OBLIVION is probably my favorite sequel.
I enjoyed PHANTASM: RAVAGER, but do not buy this "final chapter" stuff. The whole film seems to be building toward one particular character death -- in a sort of echo of the end of the original film, saying Jody died in a car crash -- but then rips it away in a final credits tag. RAVAGER absolutely ends on a cliffhanger, and definitely provides less series closure than OBLIVION did.