All lines spoken by Marth in Melee/Brawl/Wii U and 3DS are in Japanese. These are what they all are translated:

Marth's taunt - "Everyone, please watch me!" ("みんな、見ていてくれ！")
Marth's counter - "There!" ("そこだ！"), "I won't let you!" ("させるものか！")
Marth's victory poses - "This time, victory is mine, right?" ("今回は僕の勝ちだね。"), "Today, too, I managed to survive." ("今日も生き延びることが出来た。"), "There's no way I can lose!" ("僕は負ける訳には行かないんだ。")

He also has an unused sound file in the Debug Menu of the game which is "Let's Dance!" ("レッツダンス！")