I think you have a few variants:
1. "Ти менi подобаєшся" - sympathy for somebody.
2. "Я люблю тебе" - more strong feeling. It is used usually for relations, nearest friends, boy-friends or girl-friends. Also it is used for inanimate things (motherland, language etc). But you must be careful using this expression.
3. "Я кохаю тебе" - only romantic love.