Formal:
* Kocham cię bardzo. (This is the most direct and common translation)
* Bardzo cię kocham. (Similar to the above, but with emphasis on "very")
Informal:
* Kocham cię strasznie. (This translates to "I love you terribly" and conveys strong affection)
* Kocham cię nad życie. (This means "I love you more than life" and is very romantic)
* Uwielbiam cię. (This means "I adore you" and is less intense than "kocham")
Other options:
* Jestem w tobie zakochany/zakochana. (This means "I am in love with you" and is a more poetic way to express love)
* Ty jesteś moim wszystkim. (This means "You are my everything" and is very heartfelt)
The best way to choose the right phrase depends on your relationship with the person you are speaking to and the context of the conversation.