It depends on the show and what you mean by "realism". What I tend to lean more towards is subtlety of performance - cartoonishness puts me off. I can only take so many shows where it feels like I'm being harassed by the actors to laugh uproariously. Even in my nosebleed seat at Matilda I felt this, particularly with the Wormwoods, which made them seem unthreatening. I think what it comes down to is more the management of what the action on stage is meant to represent to the audience, and directing the audience's participation. I always think of Richard III, where at the beginning he's a wicked, sly joker, and as the play goes on he becomes more and more embroiled in his own drama, and our collective participation as voyeurs shifts.
I'm probably not making myself totally clear but to put a long story short, I love being able to sense a character behind the performance.