These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Contested Sequel: It's often debated whether the second and third movies were worthy additions, or if it would have been best to let the first movie stand on its own. Even people who believe the first film to be far superior can't agree on whether Cube 2: Hypercube or Cube Zero was the better sequel.
Hybercube might have retained the mystery of the Cube, was more serious but far less gory, and had a unique look, but still had some silly characters and Narm scenes. (Sean Hood's original proposal script for Hypercube was on par with Natali's original; better characters, consistently darker mood as the plot goes on and actual, constant danger.)
Cube Zero visually retained the industrial look of the first film and was far less serious with more humorous scenes than either previous film, and left little to no mystery at all, but heightened the gore in places and at least attempted continuity with the first film.
Contested Sequel: On one hand, it's got a lot of unique ideas and it expands the story a lot. On the other, it's rather poorly acted, the dialogue is extremely cliche (especially compared to Cube 2), and it manages to be even less believable than the other two.