Well, I got the impression they did kind of answer the question of where the ship went: Hell.
My opinions of "Event Horizon" are kind of mixed. The basic premise is that they were working with what amounts to a Jump Drive system which allows you to rapidly cover a lot of distance by crossing over into someplace else where relative distance is different and then jumping back into your initial dimension when you reach the point where you want to be. The old question of "what is in Jumpspace" is something that has been around since the concept first started to appear in science fiction, with it generally being portrayed as an empty void where ships occasionally get lost, and which has created some odd legends among veteran space hands but for all intents and purposes it's just bunk. Things like "Warhammer 40k" decided to take the premise of "well, what if those tall tales in those fictional settings were not only true, but things were even worse than that". The idea of ships also jumping from one world to another, rather than just entering a parallel void has also been explored both by way of intentional travel, or occasional malfunctions leading to stories similar to say Star Trek's "Mirror Universe" (in their case they mostly access it with transporters though rather than through the drive system, since Trek uses a space warping technology as it's basic concept rather than jumpspace). Event Horizon is more or less "what happenes if the only other dimension is hell, or if for whatever reason that happens to be the one you punch a hole into".
To be honest for all of the things it did right, there were a lot of details that bugged me. They were trying to be a smart movie, but rather than explaining the concept of jump space, they decided to do that hokey thing (mentioned here) with Sam Neil folding a piece of paper, probably because the director thought that looked cool when he saw it before, and felt nobody would notice. The problem is that when your dealing with a movie that's trying to be smart you can't also direct it assuming the audience is dumb, especially when the whole premise revolves around the nature of the technology being used.
That said, I think the movie probably could have also used some better pay off. See it did the whole "facing your innermost fears" thing pretty well, but that's already happened in movies, both good ones, and rather bad ones. I mean heck "Full Moon Entertainment" has even gone there with Shadowzone if I remember, and this approach to a supernatural occurance has become almost a haunted house clique... and that's kind of the problem with Event Horizon, it's a clique haunted house story set in space.
This does not mean that the movie is bad, I think it's okay (my opinions have waffled over the years, I tend to have a slightly different opinion when I review it). It has some really good ideas and concepts.
While many people would call heresy (especially those for whom this is a favorite movie) I think it's one of those films that could stand with a remake. They have the creepy atmosphere right, but could do better with the explanation and elaboration, and I think that if they are going to do a haunted house story in space they need to pace themselves a little better, a lot of successful stories in that genera tend to start out minor but ramp up the crazy (and wild effects) as time goes on. Event Horizon does this, but I never really feel there is enough of a payoff or they get
quite crazy enough towards the end. What's more when it does go from cereberal to having an actual physical horror aspect I don't think it transitions well... not the worst I've seen, but it didn't seem to flow perfectly.
Of course I'm picking. Other people have mentioned John Carpenter here, and to be honest two of my favorite horror movies are "In The Mouth Of Madness" (also with Sam Neil) and "Prince Of Darkness" (which I think went over the heads of too many viewers). Neither of which are without their flaws.
That said, I'm not sure if Event Horizon needs a huge amount of defense despite my criticism. While it was reviewed badly it's also been highly inspirational. When I look at horror novels, RPGs, and even some video games and read comments from the creators or "suggested material" this movie seems to come up a lot. For all it's critical failures it's atmosphere, which is great, impressed people, and it sold the idea of science fiction horror to a lot of people. One of my favorite small press RPGs for whatever reason is one called "Abandon All Hope" which features the PCs as prisoners exiled from earth on a giant colonial prison ship which happens to get dropped through a dimensional hole into hell (in some of the adventures it's revealed this was done intentionally as part of an experiment). The demons in that are just as physical as psychological though... it still has a rather brutal system about watching both your guilt and your insanity ratings as things happen. It's sort of like a crossover between "Alien 3" and "Event Horizon" with maybe a bit of "Pitch Black" thrown in. Of course being small press... it's full of flaws... but without things like "Event Horizon" crazy works like this would probably never have been made.