"Te quiero" in Spanish should not translate as "I love you". "Te amo" is the actual phrase.
Te quiero has a simiar meaning, but is just not as strong. Similar to "dai suki" (not taken in literal sense, as that would be [en]"I like you" = [es]"me gustas") vs. "aishiteru" in Japanese, I guess. I don't think there's any real equivalent in English.