First and foremost are the talents of Andrezej Sekula. He may have only a few directorial projects under his belt, but the man is an excellent cinematographer -- in addition to taking on those duties here, he also shot Reservoir Dogs, Pulp Fiction, Four Rooms, Hackers, and the immaculate American Psycho. As a result, Cube 2 has a lot of very inventive and dynamic camera work; an even more impressive feat when you consider all Sekula had to work with in most shots were white walls. And not only is it a better film on a technical level, I also think the script brings to the table a lot of very interesting ideas while still sticking close to the spirit of the first film (yet it doesn't require one to have seen the first film to understand the mystery here).
Basically, Cube 2: Hypercube fell prey to people's dismissive scorn simply because it's a movie that people were never dying to see made in the first place. That's also kind of what makes me dig the movie even more, though. Sure, it didn't need to be made, but you could never tell that judging from the final project. Cast and crew alike put in all the effort they could to make a film that stands on its own and I think they did a great job. Hopefully this Movie Club (and the subsequent discussion on Monday) brings out a few more people who agree with me.