The correct translation depends on the context, but I think the English expression with the most overlap is “I love you”, with the understanding that the overlap is imperfect because the English phrase can, in some but not all contexts, imply a stronger emotion than the Spanish one.

“Te quiero” is an extremely common stock phrase in Spanish, whereas nobody really says “I care about you” in English, so I think that choice of “the best translation” is unsatisfying.