Personally for me, the order goes like this (regardless of anime or game):
1. Rena: She had always been at the top, neck-to-neck with Keiichi for me ever since I started on this series. But after Tsumihoroboshi her points propelled her all the way up as my favourite character for the series. If I'm to pick one of the characters from the series whom I can be close friends with, I wouldn't hesitate to pick Rena. Kaaii + cool detective + cunning killer + Renapan > all!
2. Keiichi: Whether as a main character or not, Keiichi had always been able to somehow make an influence throughout the different chapters of the story (良い影響悪い影響はともかく
）, but I guess the main reason why he ranked so high in my list is because alot of his beliefs and attitude towards life is quite similar to what I hold personally. People who had played through Minagoroshi would also know that he's quite the leader type too. その説得力や行動力はお見事でした。「口先の魔術師」は伊達じゃないってことですね。
３．Mion/Rika: A tie. I couldn't really decide who I like more. Mion is probably the most innocent out of all the main characters in terms of her past, it was a shame that she had to be born in the Sonozaki family, and to carry the responsibility as the next leader even though she was clearly not the right choice. Rika on the other hand has my full sympathy for her situation. The description of her tragedy in Minagoroshi, despite its supernatural element, had been very realistic.
5. Satoko: Don't misunderstand. Placing her last out of all the members of the club by no way means that I don't like her. In fact in terms of adorableness alone I think she surpasses Rika and maybe even Rena. But I think given her age compared to the other 4 (take note that Rika is more than 100 years old), Satoko is unfortunately the one who had the least character development (Actually Mion didn't really get much too, but not as little as Satoko in terms of my opinion). But alas, I take my hat off for all the bravery she had shown to me.
6. Shion: What turned me off the most wasn't the series of murders she committed (I belong to one of those who understands at least partly of why she did what she did), but the way she committed them. Murder under the name of revenge, I can still tolerate due to what she had been through. But torture is another thing altogether, particularly in Satoko and Rika's case (we may not have seen how Rika was killed in Watanagashi, but it was gruesome enough for Rika to commit suicide in Meakashi).
As for the others, I think I'll just post the list here:
7. Ooishi: He may look cold on the outside, but I like his "always consider all possibilities" attitude and his dedication towards his duty.
8. Irie: Even if it's purely for his maid fetish lol.
9. あぅあぅあぅあぅ + Rika: You might wonder why Rika-chama is listed twice, but I just don't see things working without them being together.
10. くすくすくすくす (ROFL): Made to the top 10 for being able to make me hate a character so much in such a short time.
11. Akasaka: Oh my god, the first time I posted this I totally forgot about him.
He was actually higher in the rank before, but dropped because of his uselessness despite the expectations I placed on him.
12. Tomitake: Poor guy, but his own stupidity brought him to it.
13. Satoshi: I think he would've made it higher in the rank if he had been developed more.