Well, I'm not sure for which one vote so, let's see:
Sonoko: No, she's stupid sometimes, even when it's funny everytime she teases Ran and things like that.
Aoko: No, I hate her 'cuz Kaito loves her (XD, jealous of a fictional character just 'cuz the fictional character I like is in love of her? Yes)
Akako: Even when she's a very interesting character and sometimes evil, I don't like her; after she asked devil (that was the last file I read 'cuz I don't like when some anime/mangas have things like that)
Kazuha: She's nice, it's almost like Ran just that she fights with Heiji more than Ran with Shinichi, and I would vote for her if I could see her more often, but since it's not...

Ran: Well, I'm a Ran fan and she's strong, gentle and brave, an "Angel" who even saved a killer. Besides, she knows karate and very she's very smart (she can figure out Conan's true identity, but he always tricks her at the end) So I guess I will vote for Ran.