Italian: Te amo.
Spanish: Ti amo.
It's exactly the other way around.
Please notice that you don't say "te amo" or "ti amo" to a close friend. The situation has to be very important, or critical, to say "te amo" or "ti amo" to a parent, to one's child, to a sibling. And to say "te amo" or "ti amo" to a boyfriend/girlfriend means a higher commitment.
"Te amo" and "ti amo" is passionate and deep and usually reserved for lovers/spouses. You hardly ever say, in Spanish "Te amo mucho" (literally: "I love you much"). It would be reiterative, the "much" element is included in "te amo". I believe it is the same in Italian.
For all other purposes, the equivalent of "I love you" is:
Italian: Ti voglio bene.
Spanish: Te quiero.