I want to genuinely like this movie. I really do. But to this day, I can't tell if this is a great movie concept brought down by a lot of stupid moments, or a cheesy idea elevated by some decent moments. Warp as a terrible thing? Great idea. Possessed spaceship? Makes more sense than a haunted house when you think about it. And there are some effective effects, scares, and gore moments and a number of decent performances. But then the stupid hits - characters who a moment ago realized the ship was messing with their minds suddenly start being stupid (the old "separating and wandering off" clichés). And space logic is pretty flimsy here. I know that the Event Horizon was built more for being scary than practical, but the design doesn't make any practical sense.
Still, I tend to think of it as a guilty pleasure. If you can ignore the numerous issues, it's not bad. I just don't think it's some unappreciated classic.