I just picked up the new Riddick game today:
The Chronicles of Riddick: Assault on Dark Athena
First off the short version: I like it!
Now the long version: Its too similar to their previous game The Chronicles of Riddick: Escape from Butcher Bay which was one of my favorite games on the original Xbox. In fact I was really upset it wouldn't run under the Xbox emulation on the Xbox 360. Imagine my surprise when my local Game Crazy rep. told me that it was also included with Dark Athena!
Seeing them both, side-by-side, really shows how similar they are. They both are stealth shooters with bouts of face paced FPS goodness. Dark Athena takes place right after the events of Butcher Bay so if you haven't played the original it would be best if you did.
My one complaint is you can't play both at the same time as they both use the same "last checkpoint" slot so if you want to switch between them you will have to start at the last Chapter start even if your in the middle of it.
So anyhoo the games are basically the same in function and look and feel. Dark Athena does have some new weapons but other than that they are identical. Even the story is similar: "Fight the man, do side missions, escape" Dark Athena does have a multiplayer element but I haven't played it yet.
That is okay though! The game is awesome and I don't mind it one bit. For those of you looking for something different - look elsewhere.
For me the fact that Butcher Bay is included was worth the price even if I never played Dark Athena.