Oh I never answered in this thread. BAD! Well here it goes:
Favourites:
PSI: Alis; not sure why, but her character got to me the most. Probably because I spent some time with her alone (OK, that sounds just wrong) at the beginning of the game. She's the only character that you play with alone and I did so for a while since I walked around and leveled a lot in my first PS run. Also because I couldn't get passed those guards until I found the Roadpass by chance (being annoying and persistent actually seems to be a good character trait, too bad it doesn't work that well in real life). Hapbsy is a close second, I just liked his short and factual comments "We are at Gothic, please choose a destination".
PSII: Nei; you probably guessed already. I was sooooo sad when she died
PSIII: I never really enjoyed PSIII that much, thought I intent to finish it with at least one Generation 3. Can't really pick a favourite. If I had to (because the forum users put a gun to my head and told me to) I'd pick Miun. Her character was tragic, wandering in the desert for a thousand years waiting for her master to return.
PSIV: I think Kyra is my favourite here. I liked her impulsive behaviour and her desire to help the world. I really found it a disappointment she only stays with you a relative short time. Alys is a close second, I liked her * hunter mentality.
Least favourites:
PSI: This is tough, I liked most characters in the game, even Lassic. When I first played the game he still was this tragic king that had the best in mind for his people but ultimately got corrupted because he was afraid of death, something inherent to must humans I guess. I didn't like the retcon on him where it now appears that he actively sought out PD/DF to gain power. I liked him more as the benevolent king who was seduced by others, preying on his fear of death. I guess I didn't care that much for the assistant since he was pretty useless in the game and indeed rude. You go get him, then has no further use in the game. Of course the same thing could be said for Dr. Luveno but you have to visit him multiple times and he seems to be a likable mad scientist type, bit like the Doc from Back to the Future.
PSII: Neifirst; she killed Nei
PSIII: While I didn't like the game and not particularly liked any of the characters, I also can't form a particular dislike for any of the characters, probably because I haven't played it that much. Put a gun to my head? I guess it might be Rhys. I'm not sure, I found him a bit annoying, wanting to condemn his people to war because of a woman.
PSIV: I think this has to be Chaz; up to this day I wished Alys had jumped and missed and Chaz would have been struck by the Black Energy Wave. He was annoying (as was Rune, but Rune is *) and needed much pushing into the right direction before he finally takes it up upon himself to do what is right. Maybe he may be better than Alys, who started her campaign from a point of vengeance, in that aspect, but I don't know...he seemed to whiny. I just couldn't attach to the character. Gryz is a close follow up. He didn't seem to fit in that much. I thought he wasn't much more as a token Motavian because they had to represent minorities. Same could be said for Raja, but I found him to be more fleshed out with his consistent bad jokes and relations to other Dezorians (he was known by a few).