If you guys can't see the difference between these last two images, then there really isn't much reason for me to try pointing them out for you. Nevertheless, I'm going to give a try to explain my reasons; even though some of you clearly don't deserve the effort based on some of the comments.
In sculpture, there's usually a 3-level approach to form. Primary forms define the general shape of something, like a character: arms, legs, head (these can usually be approximated by boxes, cylinders and spheres). They're also called low frequency details.
Tertiary forms are the various surface textures, like skin pores and wrinkles and veins, dents and scratches, bolts and wires etc. etc. These are also called high frequency details.
Secondary forms lie between the two and are what really give character to a sculpture. A good piece of work also balances the three main levels of details with each other in a harmonic fashion, and use them to guide the eye around the piece.
The trolls on that GOW3 picture are quite obviously missing good secondary forms. There are some simple large shapes and some high frequency detail, but there's almost nothing between the two.
This can also be said about most of the other elements of the scene, including the chain links, the floor and walls, and to some level, even Kratos.
There's also been a comparision picture of Kratos and Beowulf, and the same can be said about the faces. Kratos has the big forms - nose, cheekbones, brows, mouth etc. - covered, and there's an appropriately high resolution skin texture thrown on top of it all; but the transition between the two levels is once again abrupt . The upper bodies aren't in such a big contrast, but that's due to the strange shapes on Beowulf - the muscle sim (and pretty much of all the animation and rigging) in that movie was quite off the mark.
It also bothers me that most of the high frequency detail seems to be created by taking some existing texture and just throwing it on top of the model. It's either a photo texture with some Photoshop work to disguise it, or some generic 'metal' and 'skin' and 'elephant skin' stuff.
But in reality, these tertiary forms are created through some process, which effects their placement and general look. Dents and scratches appear more often at places where a weapon may get into contact with something (in case of a sword, the edges), skin pores and wrinkles develop based on how the tissue is pushed and pulled over the muscles and bones, dirt gathers up in recesses. All this can be replicated when an artist takes charge and decides where and how to create these details - just applying a 'metal' texture won't be enough.
Once again GOW3 displays randomly placed details, many times not appropriate to the nature of the given object.
Then there's color, which I'm not that much into, being a modeler and not a texture artist; but suffice to say that similar issues would be discussed with regards to primary and secondary colors, how they complement or contrast each other, and also saturation and balance and harmony. Then there are the surface properties - how strong the specular highlights or reflections should be, also depending on the wear and tear, and should they be sharp or soft. And of course the art style should be maintained through all parts of the game, despite having dozens of artists working together with their own individual approaches and preferences.
Then there's putting it all together with lighting and effects - how much key light, how much fill, how to set their color, how sharp the distinction. GOW3 here is very rough again, lots of sharp contrast with a lot of overexposed highlights and plenty of bloom to emphasize it even further. All this combined with sharp shaders and normal maps and little fill light.
In the case of the Darksiders screenshot, I consider most of the above mentioned issues to be covered properly. Plenty of interesting forms and shapes balanced out nicely, lots of color that's used very carefully, soft lighting that still has enough contrast to properly bring out all the secondary forms in the normal maps, and so on. They also make sure to manually darken the textures in areas that are not supposed to receive light, so you don't get bright inner mouths and ears, fluorescent teeth or stuff like that.
It also helps that the designs are usually more creative and ambitious, even if not that original. Check out this gallery from one of the concept artists:
http://autodestruct.com/concept.htm
Obviously, taking proper care of all these things takes a lot of time, constant iteration of making changes and checking them in the engine, and so on - this is the most expensive part of asset creation (not the software, hardware and such).
So, I'd say that the most likely reason behind the quality difference between the two games is quantity; GOW3 will probably feature more types of enemies, larger levels, and thus there's less time to spend with each individual asset.
It also has to matter that Darksiders is Joe Mad's pet project and the man himself is a successful comics artist - so he probably spends quite a lot more attention on the artwork in his game.
It's also interesting that the first two GOW games were much more like Darksiders, spending a lot of time on making each piece of art look as good as it can, maximizing the texture and poly budgets and creating a softer light with more ambience. Which is why I consider the sudden transition to new technology another issue - Joe's team members, at least the ones I know through various CG art forums, have already had experience when they've started. And of course the game has spent more time in development, having been announced in 2006 or so; although I have to mention that most of the stylistic elements and the general level of polish have already been there.
