[Trouble]

Do NOT use Aishiteiru. It freaks them out and it makes an awkward barrier inbetween you two forever. Trust me. It's sometihng you'd find in movies and TV. Revert to (Name here) ga suki desu/da, depending how much you know this person. It literally translates to (Name) like, since "I" can be ommitted, watashi is left out.

Bottom line: Say "(Name) ga suki desu"