Ranma, of course, MI, and no one really cared if humanity was on the brink of destruction - we were only concerned with Rick, Lisa, and Minmei. Full Moon, yes, Fruits Basket, sure. But let me think of some titles that haven't really been mentioned.
They Were Eleven had a sweet, yet a bit unconventional love story. Nadia had love themes throughout the entire series, both mature and lighthearted. Record of Lodoss War had some distinct pairings.
But I think my favorite anime for romance has got to be Saint Tail. Meimi and Asukia Jr.'s relationship is very sweet, and I love the scenes with Meimi's parents. I think they're my favorite anime couple. *sighs dreamily*