Formal:
* J'ai beaucoup de chance de t'avoir dans ma vie. (I am very lucky to have you in my life.) - This is a more formal and polite way to express your feelings.
* Je suis très heureux/heureuse de te compter parmi mes proches. (I am very happy to count you among my loved ones.) - This is a less direct way of saying you are lucky, but it still conveys your appreciation.
Informal:
* J'ai de la chance de t'avoir dans ma vie. (I am lucky to have you in my life.) - This is a more casual and friendly way to say it.
* Tu es une vraie chance pour moi. (You are a real blessing for me.) - This is a very affectionate and personal way to express your gratitude.
* J'ai beaucoup de chance de te connaître. (I am very lucky to know you.) - This is a more general way to express your feelings, but it still shows your appreciation.
For a friend:
* Tu es un(e) ami(e) en or! (You are a golden friend!) - This is a very affectionate way to say that you are lucky to have them in your life.
* J'ai tellement de chance de t'avoir dans ma vie. (I am so lucky to have you in my life.) - This is a more heartfelt way to express your feelings.
You can also replace "dans ma vie" (in my life) with "à mes côtés" (by my side) or "dans mon quotidien" (in my everyday life) depending on the context.
Remember to adjust the tone and language to fit the specific person and situation.