I was watching James Bond: Skyfall last night, and it felt darker than the previous films. I vaugely remember watching other James Bonds in action, as well as one or two of Craig's Bond before.
While Craig's Bond seemed to be less whacky, and more realistic the other Bond movies (perhaps due to technological advancements achieving more and more of the impossible), Skyfall seemed to showcase the darkest of Bond yet.
He appeared visibly thinner after his re-emergence from retirement. His failure in the various tests required by MI6, and the strain in his right shoulder raised questions about whether he should still be a hunting rat. It showed that he is still human, capable of losing his edge (perhaps due to age). All that makes for a rather intense Bond movie. Enough to keep me watching into the wee hours.