The German version of "Happy Birthday to you" is Zum Geburtstag viel Glück, zum Geburtstag viel Glück, zum Geburtstag, liebe(r) [name], zum Geburtstag viel Glück! You have to replace [name] by the name of the person. But frequently the song is sung entirely in English in Germany. There is also a different German birthday song with a different melody: Hoch soll er/sie leben, hoch soll er/sie leben, dreimal hoch! If you search on youtube I am sure you will even be able to find "live versions" of both of these songs. I also found a webpage which collects a number of not-so-much-standard birthday songs: http://www.festgestaltung.de/geburtstag/lieder1.shtml

"Happy Birthday to you" is really popular and famous I don´t think there is a good and popular translation People know the english text and sing it sometimes you hear an older( traditionel german) song sung with other tones ! Hoch soll sie leben! (Long may she live!) Hoch soll sie leben! Dreimal hoch! (Three cheers!) or Hoch soll er leben! (Long may he live!) Hoch soll er leben! Dreimal hoch! (Three cheers!)

Knut is right "Zum Geburtstag viel Glück" is a way to sing " Happy Birthday" [ but the translation is really bad ]