The Romans had a saying, "De gustibus non est disputandum." It translates as "regarding taste, there can be no argument." It carries a similar sentiment to "beauty is in the eye of the beholder." Personally, I would say that Lisa is my favorite character, but I also like Alice and Ann. I find the Olivia and Lisa route hotter than the Lisa girlfriend route, even if it has less content at the moment. My least favorite girl at the moment is Kate. I find Kira at this point to be pretty boring. She is more of a McGuffin than a character. Still, I would greatly like to see her character fleshed out and more content with her added.
Still, DS has done a great job with this game, and I can certainly see why others would have different views than myself.