I think I should mention exactly why EBA's "A Christmas Gift" (You're the Inspiration) sits so well with me.
It's that it's believable. That's really all about it. The situation that happened, the other character's reaction to it - it's all realistic. And that makes it all the more powerful. There's no end of the world, no apocalypse, no life-or-death situation, it happened on a normal, every day life. And then Lucy's failure of actually grasping what exactly happened, coupled with her mom's emotional state, it's all realistically depressing. The subtlety of it, leaving the player to interpret what happens, holds it together. And the sweet ending, oh god, it might throw away the realism I spoke of for brief seconds, but it's still left to the player interpretation of the whole thing and the way it was done really packs a punch. Seriously haven't seen a single person who didn't react strongly to it.
And that's not taking into consideration the song itself and the agents. Normally the game is so whacky and fast paced, with songs that just pump you up to the rhythm with the agents having some wicked dances. This one is an exception, and completely unexpected. The song is slow and sweet, and the agents, instead of normally dancing, they just stand, wave their arm slowly (as encouragement) and hold the microphone close as if they're singing, which is actually rare. This actually makes it a lot more powerful. Hell even the Divas, where contrary to Agents having unique dances, have the same exact dance routine for every song but make it an exception in this one song and do the same as the agents. The fact Commander Khan didn't say his usual catchphrase before the start of the song (Agents are GO!) in this particular one also holds. This level of detail is amazing.
Personally as well, I'm not a father, but I have a little sister and many little cousins who I tend to care of, being in a big family and all. I completely sympathized with what happened.