I think Naru from Love Hina, oddly enough, probably because she was the main heroine and wasn't _unpretty_. Or Motoko, maybe because young Asian women with katanas/knives are beautiful (see Shiki Ryougi).
wow, this is a tough one... the American cartoon's Raven from Teen Titans is fairly early on my love of 2D girls... I'm not sure if I liked Misty from Pokemon in that way... maybe Mai from Popotan would be my best guess since that's one of the first Japanese animes I've seen.