I'm often asked for end-of-year greetings in Korean (not so often Japanese). I came across these two translations recently. They are much better than trying to literally just translate "Merry Christmas" or "Happy Holidays" since neither of these short expressions exist in Korean (and presumably Japanese). I should also point out that these written greetings are way too long for reciting orally.
기쁜 성탄과 희망찬 새해를 맞이하여
건강과 행운이 함께 하시길 기원합니다.
Literal meaning: "I wish that you have a merry Christmas and hopeful new year, along with health and good fortune."
Literal meaning: "Happy New Year. Best wishes for a peaceful, joyous, healthy and prosperous new year. January 1, 2012."