Lol not reaaly not every girl he come acorss fall for him. Its Only Touka,HInami(though only see her as big brother),Eto and Itori I think,It just Kaneki is kind and caring which some people like Touka and Hinami really likes. While others for different twisted reasons such as Eto and Itori.
Lol I don t think Kaneki is harem protagonist