I think his face here looks so so sad, because as this other person pointed out, he is not much accustomed to dealing with death, and it grieves him(Also people stop hating on Legolas you bunch of elf-hatin losers!
Lord of the Rings Final count Fourty-two? That's not bad for a pointy eared Elvish princeling. I myself am sitting pretty on Fourty-three. He was twitching because he's got my axe embedded in his nervous system! Legolas and Gimli