This a topic!
Now my memory isn't to good with The original and R because i was only seven at the time. So I'll try my best.
Original: Nephrite. He was just cool! No more to say. I cried like whoa when he died because he save Molly.(Naru?)

Even though I wish she would have shut up. I hate her dubbed voice. OY!
From what i have heard Berryl was cool to. But sympathize for me. I never saw the final battle with Berryl to this day. OH THE HUMANITY.
I cant spell it but When Mamouru was turned evil by Berryl. when i first saw it i was young so i thught it was just horrible but now i think it was kinda cool. I was really gettin tired of Tuxedo Mask's corny speeches. Let the senshi get out of their own mess please. Wait till it is absolutely crucial then come. that cut down on your talking at least.
R: Alan and Ann are my all time favorite villians ever in any anime or manga ever invented. The episode when Mamouru put on the play of Snow White is my all time favorite.
Black Lady was just cool. nothing left to say.
Saphire and Diamond. I just liked em.
Rubeus. Catsy, Prizma and their sisters whose name never actually came to me.
Fiorre and Kasinian. The first movie was my favorite of the three.
S: If Sailor Saturn was a villian then that was my favorite. I love Hotaru. She has the most gorgeous eyes i have ever seen in any anime.
SS:Nehelania was nuts. But the trio and quartet were cool.
Stars: All I have is the first volume of manga. but I already like Galaxia. I don't know her life story or anything but i love her character design. She's gorgeous.
I apologize for how exceptionally long this post is. *crawls on knees and begs for forgivness*