Formal:
* Je t'aime infiniment, mon amour, tu es ma vie. (This is a very formal way to say it, emphasizing the importance of the person in your life.)
Informal & Passionate:
* Je t'aime tellement, mon chéri/ma chérie, tu es ma vie. (This is a more informal and passionate way to express your love, using "chéri" for a male and "chérie" for a female.)
Informal & Poetic:
* Mon amour, tu es ma vie, je t'aime plus que tout. (This is a more poetic and heartfelt way to say it, emphasizing the importance of your love.)
Other options:
* Tu es mon tout, je t'aime. (You are my everything, I love you.)
* Je t'aime à la folie, mon amour. (I love you madly, my love.)
Ultimately, the best translation will depend on your relationship with the person you are speaking to and the context of the situation.