I'm not picky, but it's one of my favorite movies. Not sure what my selectiveness has got to do with that at all.
What sets it apart from most modern comedies? Everything, really. The humor and the characters are not watered down. It sticks to it's style and the era it portrays. It's spontaneous but never awkward. The actors know what they're doing and are totally into their characters. Really, I think it's up there with American Hustle as one of the all time best crime comedies.
I haven't watched TBL, but I found American Hustle a pretty mediocre movie. It has an outstanding cast - wasted on a terrible, terrible pacing and story-telling. I struggled to watch the movie once.
Makes me imagine I won't enjoy The Big Lebowski either.