Exactly! An encounter like this would be pretty pointless if you used an abstract system of any kind to resolve it.There's only one way to do this old school: Have the players recite poetry then and there. Depending on the players, they may either proclaim, "This is the best encounter ever!" or they may stare coldly into your eyes with a sense of WTF! This depends on if the DM can guess if the players would enjoy such a thing. If he thinks yes when he's wrong then that may lead to problems.
Essentially the skill-challenge aspect would be the background/in-game information gathered, etc. When it comes to social skill-challenges.
So the players would actually recite the actual poetry and me as the Giant would as well.
But the players would also roll to determine some things.
-Recite a poem, then roll to see how well their character was able to perform it, (diplomacy)
-Insight see what the Giant thought of it (give hints, information or misinformation if done badly).
-Bluff would be done to give players time to come up with a new poem, or intimidate, etc.
So basically while it would be actually roleplayed and acted out in-game things that determine how much it actually helps is somewhat determined by the dice.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.