It's unfortunate that this movie a) came via Frank Miller, 2) followed Sin City (chronologically), and iii) used a very similar visual style to Sin City, because a lot of fans expected something virtually identical to that film. When they didn't get that, boy howdy was there payback with the reviews and ratings!
But if you look at the source material (and the era of such) and then let the film show you its own intention re: style, you will end up really digging this.
One key is not to take it too seriously. I mean, a line like “This one's for Muffin!”, even delivered WITH the straight face, should let you know how you're supposed to receive it!
A favourite of mine – a guilty pleasure, yes, but it's a ‘keeper.’