Expectations were high after the brilliant Escape from Butcher Bay. Sadly, Assault on Dark Athena fails to deliver.
Let me get this out of the way: Assault on Dark Athena in no way approaches the greatness of the first game. The graphics engine received an update (the game comes with a revamped version of Butcher Bay, by the way) but to be perfectly honest, I barely noticed any improvements over the original. And that's fine --the original's graphics were plenty pretty-- but it seems that this small bump up in terms of graphics comes at a cost. To put it simply: Dark Athena feels sluggish and unpolished.
Gameplay-wise, the stealth and especially the roleplaying elements that made Butcher Bay great have all but disappeared. There are a few sneaky bits, but conversations are rare and uninteresting, and you mostly go around shooting things in the face over and over. Nothing against pure FPS games, but Dark Athena just doesn't hold up against its competitors. (And the Bioshock homage near the end makes this fact all the more obvious.)
And finally, the plot. There is one, for sure, but it just fails to engage. Butcher Bay brought you a consistent and interesting game world filled with characters make sense and that are interesting. Dark Athena, however, is full of lifeless backgrounds for unoriginal action sequences, and littered with unlikeable and unconvincing characters.
That is not to say that Dark Athena is a bad game. It's just not all that good. If you're already a fan of the first game, only play this one if you really want to and after seriously lowering your expectations. However, if you've never played a Riddick game before, I suggest you give this one a miss and go for the brilliant Butcher Bay instead. You won't be disappointed.