A year after their spaceship crash-landed on Earth, the alien species known as 'DearS' have been accepted into the Japanese citizenry. They are adored by many fan groups and trusted by most humans - with the exception of Takeya Ikuhara. Kind-hearted but resistant to change and skeptical of the DearS' seemingly-friendly behavior, Takeya tries to have as little to do with them as possible. But after he saves a girl from an incoming truck, and she turns out to be a DearS, Takeya ends up being far more involved with them than he could have ever imagined.
Nineteen-year-old ronin Hideki Motosuwa desires two things more than anything else: a girlfriend, and an expensive humanoid computer (known as a 'persocom'). But with his dead-end job and no financial aid from his parents, owning a persocom seems impossible... until he finds a blond-haired female persocom tied up amongst a pile of trash! After getting her home and figuring out how to activate her, even the computer-illiterate Hideki realizes there is something unusual when it appears she can only say one word - Chii. Is she just broken, or is there more to this persocom than her behavior lets on?
Both manga are slice of life sort of magical girl manga, where the female protaganist slowly develops over time starting from scratch.
Both manga feature a non-human, android-like girl and in both of those series the girl is a kind of a defective product. The male lead (who is made to live with the girl) finds her to be great annoyance at first, but slowly starts developing feelings for her later on (he certainly doesn't think of the girl as defective). Both series pose as ecchi comedies, but they actually contain some drama and obviously romance. If you liked one of them, there is a big chance that you will like the other one as well.
Both are futuristic (to a degree). In both series, the non-human beings are predominately portrayed as female, which allows the for the ecchi themes, along with the down-on-his-luck male lead. They also both illustrate similar relationships, which leads to some questioning of whether humans and non-humans can love each other. There are other more basic similarities, but I think that if you enjoy one series, you should consider checking out the other.
So, in this alternative reality some sort of non-human being (the Dears in case of DearS and Fairia in case of Fairial Garden) is all the rage among the population. Everyone, but our male lead, wants to have one of those. Yet, it is him who comes into possession of a special one (much to his dismay). From there, despite his initial negative attitude, he gradually starts to care about the one in his care. Note that Fairial Garden is awfully cute and unlike DearS it's ecchi free. If the first part of this recommendation got you interested and the second part didn't discourage you, you might as well give those two manga a go.
After his apartment burning to the ground and almost being killed by a falling metal object, Ohmura Takeshi is ready for the afterlife. Luckily, a beautiful angel appears to heal his wounds and inform him that if he stays with her, no harm will come to him. The catch? His long-lost deadbeat dad has passed along a curse: he will experience nothing but sadness in his life. Now, after changing to a human to maintain close contact, Elle will stop at nothing to make sure that a bit of happiness comes into Takeshi's life, but not before first learning how to be a human!
Happy World! follows a similar concept. Like DearS it features a non-human girl who decides to live with the (un)fortunate high-school boy for one reason or another (much to his annoyance). If you've read DearS and want to read something similar you could give Happy World! a try, though it's probably not even half as good as DearS.
Maybe it's just me, be Fantasy Maid, looks similar to DearS, except the characters seam more likable and ecchi seems to have been replaced by cutness. This is just a hunch, but my gut tells me you might like Fantasy Maid if you liked DearS (especially if you'd like it more with less fanservice).
Edit: Actually there is a bit of smut later on in Fantasy Maid...
Takaya is the strongest and most handsome guy in school, but also the most misunderstood. His life is irretrievably changed one day when he finds a mysterious pendant and opens it - to his surprise, out pops a beautiful girl with F-cup breasts and wings on her back! Her name is Lilim, she's a succubus, and she also happens to feed off the life energy of humans. Unable to seal her away again, Takaya persuades Lilim not to feed on others, but to stay with him and only take his life energy. However, is Takaya really prepared for the consequences of having a beautiful, live-in succubus interfering with his life?
There is this delinquent dude in whose life this non-human girl appears. She moves in to his house and annoys to no end, but he somehow gradually comes to love her anyway. If you read one of those manga and liked it, reading the other one might be a good idea.