How about Arakawa Under the Bridge? Ok, it's not a lovecom. And to be honest the girl is not a venusian as she said but a human. But I still think it's so funny and quite interesting!
But maybe is not what you're searching for ><
There's also Otome Youkai Zakuro. Thought maybe that's too shoujo for you? I'm not quite sure. But the love story is between a human boy with a youkai girl (her fluffy ears are so cute!).
Petshop of Horrors only had OVAs and those are OLD. But I still think that those are reaaaaal great. And there are many many kind of forbidden loves there.
Seconding Fushigi Yugi, Princess Tutu, and Fruits Basket, which all have elements of romance and all are tear jerkers.
However, I gotta toss in my guilty pleasure, Shattered Angels (otherwise known as Kyoshiro to Towa no Sora). It's kind of cliche and all sorts of cheesy but, if you can get in the story like I can, the forbidden romance angles and the character relationships can get to you. It's made by the same person who made Kannazuki no Miko, which also has a forbidden romance angle and is definitely a tear jerker.