I feel like some of us are overestimating the dramatic power of Stannis' sneak attack. Yes, defeating the wildling army is a hugely important event for both Stannis and Westeros as a whole, but from a TV drama perspective, it's not terribly interesting. Consider: 1) Stannis is not under any threat. He may be outnumbered, but he has superior resources and the element of surprise. 2) His attack of the wildlings doesn't represent anything meaningful about him as a character. Sure, he's going through the trouble because he's decided that that's what kings do, but there's no personal element to it. He's not, say, choosing to save a former enemy, or reversing a character trait (e.g., Han Solo at the end of New Hope). Compare that to the battle of Castle Black, where everyone on the NW thinks they're going to die, but still manage to succeed against all odds by believing in their cause and because certain characters manage to change and grow.
