Is that sarcasm? :P

The three films I listed have one thing in common and that is that for me they created a very good atmosphere. THAT is what scared me. Also somehow they seem to "talk" to some primal fear I have which I know is probably up to each person.
Few films I think really get the atmosphere right and connect to some primal inner fear (For lack of a better word and explanation.). One other is the original Ring. That's one creepy film. Especially if some friends of you anonymously drop a burned copy in your mailbox. :P

It wasn't that EH was bad, I just thought it was the same old thing. It had it's creepy parts but the whole movie just seemed like someone trying to recreate all the scary scenes from other sci-fi horror movies and put it into one.

I actually watch Halloween on Halloween so i wouldn't choose any of those two :)

I thought Event Horizon was rather good tbh as it made good use of the psychological state of the crew which I find rather unique, and I can't see very much how this was clichéd from other sci-fi horror movies as there aren't that much, Alien is very different for example.
I found that Pandorum tried hard to rip Event Horizon off, but I even liked that one though less than Event Horizon.

Hm. I guess we watched Event Horizon differently tinyE. I instantly got hit by the atmosphere and how well the psychological horror was handled as Strijkbout said. The whole film was so oppressive and tense.
I also can't see how it is the same old thing. Yeah it's basically the old premise of a group of people trapped in a isolated place where something dangerous is going on that they don't understand but it's done in such a good way that it feels new.

We're probably different kind of horror film persons. Some like jump scares, some ripper, some splatter and so forth. Me I like most horror subgenres it just that some gets to me much more.

I liked Pandorum too. Sort of a mix of Event Horizon and Aliens. An underrated film I think. It did everything right. Not exceptionally right but above average.

I liked Freddie Grueger.
Exorcist is OK with something jumping on the floor but still, Robert Englund..

Yeah. One of the most important things that makes me like a film is how it's filmed. Got that from watching Kurosawa and Leone. Pandorum is excellently filmed.

The Exorcist - scary scary all the way! (but only the Theatrical Version, the Director's Cut is really poopy)

Again, different strokes for different folks. I hate the original The Ring (Ringgu). It was okay up to a certain point where the plot took a left-hand turn into La-La Land. After that I couldn't take it seriously anymore, and it stopped being scary, just ridiculous.

Yeah, everyone we've shown it to have also been scared as hell. The acting really is fantastic, and the fact that I don't know any of the actors somehow makes it more scary.

The other end of that spectrum is Cube, which is also based on an interesting concept, and populated with (to me at least) unknown actors. The difference is that the acting in Cube is not fantastic. All the actors save one seem to be graduates of the Royal Canadian Academy of Overacting, and it makes the movie seem ridiculous rather than scary.

Normally I'd say to pick whichever one you've not seen already on the big screen.

As that's neither, then if it's the director's cut of The Exorcist, and you've not seen that version, definitely see that -- aside from anything else, I'd imagine it would be a newer print given the recency of that version of the film, and therefore would likely look better on the big screen than ANOES will (although I confess I'm speculating wildly here).

And as for criticising the new cut of The Exorcist vs the original, there's only 10 minutes difference between them (the new cut being the longer one), so I really don't believe you'd love one version but hate the other. Sure, you'll have a preference, but it's essentially the same film.

Failing any of that, flip a coin? (and if you're disappointed at the outcome, pick the other one :)

i would probably go for nightmare, because it's more on the silly fun side and it would work better in a crowded cinema, exorcist is more serious and a slow burner too.

I prefer the director's cut of The Exorcist, because it is a bit more developed, a bit less of a downer, and a bit closer to the book.

Is Cube the movie where they are trapped in the box that keeps changing? I think I saw the sequel a few years ago; brilliant concept and I enjoyed it but I considered it more sci-fi suspense than horror ie in the vein of a Logan's Run as opposed to an Alien.