Pitch Black is at least twice the film that Riddick is, although it is really unfair to compare the two. As has been said here already, they are two completely different films.
Riddick seems intent on "wowing" the audience from the start, with big special effects and a plot that doesn't really matter. That isn't to say that Riddick is a bad film, it is just that Pitch Black is superior in every way (except, perhaps, in terms of SFX, but that doesn't really concern me).
I guess it was confusing due to the fact that Pitch Black was remarketed as Chronicles of Riddick: Pitch Black when the sequel came out at the cinemas.
both films are great IMO. David Twohy (director of Pitch Black and Chronicles of Riddick) has come a long way since his days of directing Charlie Sheen in the Arrival (another great Sci-fi flick). Has anyone seen Arrival II?
I thought Karl Urban was pretty cool in Chronicles of Riddick, since this was his first film post Lord of the Rings as Eomer.