I never really got the impression that D:OS was "looney toonish," honestly. I thought it had a healthy portion of comedy in it but most of that was in the dialogue and the ridiculously stupid things some people would say or do (which struck me more as satire about the stupidity and gullibility of people in general).
Overall the game seemed to have a good story and plot that didn't take itself too seriously.
D:OS2 has a much more "dark" tone it so far from what I can see, there's much less light-heartedness to the dialogue and goings-on but there's still a sprinkle of humor because dark, morbid and depressing without the occasional comic relief gets cumbersome.
