Graphics, sound
Although it's a stretch to call Riddick's lighting as good as Doom 3's, the style is comparable. Escape from Butcher Bay doesn't have per-pixel lighting like Doom 3 did, it's per-vertex like Half-Life 2. However, like Doom 3, Riddick makes extensive use of it, especially of deep shadows, dark corridors, and so on. Now where Doom 3 shuts off the lights in order to have monsters pop in from closets behind you, in Riddick, you are the monster.
The game makes some use of the third-person perspective, typically in cutscenes or whenever Riddick has to climb a ladder or crate, or swing along junglebars. The perspective is often helpful, but the camera is partially locked and sometimes blinds the player to new threats from an unexpected direction. It's best to keep your ears open whenever climbing up to a potentially hostile area.
Animations are very smooth and quite realistic, and deaths do have ragdoll physics. In fact, especially at higher difficulty levels, the ragdoll physics get quite a workout as the player finds himself dragging enemy corpses around to hide the evidence of his misdeeds. The models are a little on the beefy side but generally proportional and to scale - Riddick in-game is a veritable clone of Vin himself. There is generous use of shaders and normal mapping for a gritty, realistic feel to it all. Some levels could stand to use a wider color palette, but it's nothing to get hung up about. The most serious flaw is the persistent appearance of seams between textures on character models.
Sound is solid without being particularly excellent. Vin Diesel lends his voice generously, for both cutscenes and the character's private thoughts. In fact, all the voice acting by major characters is quite good. The chemistry between the characters of Riddick, Johns and Hoxie is remarkable for a video game. It may not be 4-star movie material, but it is unparalleled in video games. Riddick and Johns in particular show a familiarity that's not just evident by the background story, but the way the voices interact.
The music, like the rest of the sound effects, is high quality and non-intrusive. It's not good enough to sweep you away but it's also not bad enough to stick out like a sore thumb. In the words of Goldielocks, it's just right.