The sequel switches genres once again, revealing that Riddick lives not in an Alien universe but on the outskirts of a very dark Star Wars one (or maybe even a Flash Gordon one), and turns him into Conan/Kull the Conqueror. They sort of can't be seen as sequels, even though they absolutely are, but I enjoy both of them on their own merits; if you had to pick and choose, though, Pitch Back would absolutely be the keeper.