Entertainment value ? That it has. But it fell into the trap of wanting to do too much. The whole concept of the Underverse-Necromonger-Lord Marshal is really bad. And their design is terrible. Plus it is way too much to add, to what was Pitch Black. If they are around for such a long time and they obliterated Riddicks people why had he never heard of it. There are just too many gaps to make this believable even in the terms of a SciFi concept. It also didn't mix well with the whole Riddick/Jack (Kyra) part.
Supporting characters are weak. A manipulating woman that tries to put her husband into power because she can't do it herself. That's a walking cliché. So is Toombs who tries way to hard to be the tough guy. The action is good and Riddick has once more some memorable one-liners. And going back to the husband - Urban's character is totally forgettable. Which I almost did already.
I also want to go back to "Dark Fury" once more. Nothing that was in that animation is pertinent for the story. You would've no problem following the plot if you haven't seen "Dark Fury".
I'm struggling to rate this as a "7", it really more of an above average "6".