The link to WH40k seems pretty weak for Event Horizon from my point of view. "nasty shit waiting for us in another dimension" is pretty standard fare.
Cliver Barker's stuff is much more clearly influential on the series. As is the Alien franchise.
Warhammer 40K started with this particular schtick somewhere between 1987 and 1993 (as the first edition got compiled), IIRC. Event Horizon was 1997. So
spiritual predecessor, but certainly not
temporal.
(Hellraiser was 1987 [ninjaed, with more detail!], The Thing From Another World was 1951. But, even there, I tend to agree with a 'common originating meme' and/or 'converging evolution', rather than a direct link. OTOH, non-40K Terminators doubtless inspired the 40K Necron race (while 40K Terminators were at least a distant great-uncle of Halo Spartans) and Manga (especially that featuring Gundam-like mecha) probably inspired the Tau. The original Gene-Stealers were Aliens (but the Tyrranids as a whole predated at least the
filmic Starship Troopers, even if not the original 1959 book, which might have also inspired aspects of Space Marine tech). And of course a whole swathe of 40K races are future-versions of the original Warhammer races which are basically direct descendants from Tolkien, with the benefit of many decades of intervening derivative fiction and popularisation of the appropriate concepts in the appropriate melting-pots made of adolescent human brain.
Mmmm... adolescent human brain.... <droool>)