Wishing you a very Happy Birthday and many Happy Returns for the day.

Happy Birthday XXXX! May you have a wonderful day today and may all your dreams come true. Best wishes from YYYYY

Happy birthday to you, Only one usually.

I wish you a happy birthday!

Generally, we speak "祝你生日快乐(zhu ni sheng ri kuai le)". if the person is a elder or your seniority, we speak "祝您寿比南山，福如东海（zhu ni shou bi nan shan，fu ru dong hai）