Event Horizon was a good horror movie. I don't know why some people hate it. It's not like horror movies have high standards. Unlike most horror movies, Event Horizon was actually scary, had pretty good acting, and had good looking visuals.
Serenity was just a so-so movie to me. I've never watched Firefly so maybe that explains my lack of enjoyment in Serenity. What's funny is that my first thought about Serenity was that it seemed more like a 2 hr TV special than a theatrical release even though I didn't know about Firefly.