The Fifth Element.
It's really held up over the past twenty years and Gaultier was on point with those costume designs. I think I like it because as well as being an entertaining watch, it was visually spectacular. I really liked the level of detail and thought in it, which is probably why it's not turned into a clunky dated disaster. It's an art film as much as a sci-fi.
I also really like The Cell. You can say what you will about JLo's acting, but the entire aesthetic of it is stunning, albeit a little twisted.